Hey all... I'm having a bit of a problem with my '88 305 TPI. It has a hard time starting, whether it's hot or cold, unless I mash the pedal down to the ground. It doesn't even matter if the car has only been off for a few minutes. It usually takes a good 2-3 sets of cranks (just a few seconds a piece) to get it started - again, less with the pedal pushed in.

I think I remember that "flooring" the gas pedal during start-up will cause the car to go into a sort of "clear flood" condition. Is this true?

If that's true, then I should be looking toward leaking injectors or fuel regulator, right? Any other advice? Perhaps it's a bad computer? - John '89 L98

 

John,

Yes, opening the throttle beyond 80% is a "clear flood" condition where no extra starting fuel is provided regardless of cooland and intake air temperature.

Most likely you have a leaking injector ir two. Monitoring the fuel rail pressure after shutdown will tell you what's happening. The pressure should remain for several days.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Vader, thanks for the advice. I was able to pick up one of those Actron Fuel Injector testers for 4.49 at the local Sears Hardware that is going out of business. I guess he was in too big a hurry to realize the original price was 44.99. Oh well, my gain.
Anyway, I'm gonna check out the injectors later tonight. I'll post my results.

Without making this too long, I guess I should also mention a couple other things. First, the fans kick on whenever they damn well please. Sometimes it just the passenger-side, sometimes it's both. Looking at my Diacom over a 20 minute period, the coolant temp rises in the beginning, but stays level throughout the capture. The fans, on the other hand, will turn on and off with no rhyme or reason. I've tried switching out the relays, checked the CTS, disconnected the A/C pressure switch, check to see if the redundant fan switch was grounded, and even, since it was time anyway, changed the coolant, and bypassed the TB.

Second, I have very few mods... A gutted MAF, a relocated MAT sensor, cut-out air boxes, K&N's, and an Accel Super Coil with Accel wires. I'm running Rapid Fire plugs, I'm using 89 octane fuel, timing checks out at 6 BTDC, TPS is working properly, and no codes are thrown. It's an '88 IROC convertible with the LB9. I did notice that I get quite a few knocks on the Diacom when I start up, and if I'm hard on the accelerator. Also, the car takes a longer time to idle down after start up, than my 3 other (working) TPI cars.


Sorry for the long post, but if anyone has any advice, it will be greatly appreciated. Thanks again, Vader. - John '89 L98

 

John,

That injector tester is probably just a solenoid firing test light. It's a handy tool to have but won't tell you if the rail pressure is dropping (unless I misunderstood your description of the new acquisition).

You'll need a fuel pressure gauge to do that. A refrigeration low-side gauge works well, but you'll have to thoroughly clean and dry the hose after using it for gasoline. (It's always good to clean and dry the hose, but that's another story entirely.)

None of your modifications shoudl be causing the problem. The high idle on startup is simewhat normal, but if you have extra fuel from a leaking injector, the IAC will have to close even further to try to control idle. Cold starts with excess fuel tend to cause higher cold idle.

Your fan problems aren't likely related, so tackle the starting thing first. It may be that the Diacom is causing the ECM to enter diagnostic mode, which will operate the fans. The fans also operate when the AC high pressure switch closes, so that's another possibility.

------------------
Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Vader, You're absolutely correct in assuming that the injector tester simply fires the injectors one at a time by either sending one long pulse (to check for clogged injectors), or multiple short pulses (to check for slow or leaky injectors). I used it along with my handy-dandy fuel pressure gauge (HVAC low-side gauge). It’s been used several times with no problems to date. Oh, and I try to have the woman clean and dry the hose as often I can.

Here’s what I have in the way of fuel pressure leak-down. It’ll lose about 1 PSI per minute. I only checked for 15 minutes at a time, but it was the same the 3 times I did it. I’m a bit wary of pinching off the return line to see if it’s simply draining back into the tank. Is there another way to check for leaking injectors? Hmm... Maybe I should pull the plenum off, and lift the rail up with injectors intact and physically see if they’re leaking? With the fuel injector tester, all injectors were within about 1 PSI of each other. That is, each injector tested resulted in a fuel pressure drop within 1 PSI of the others. Pressure is up around 42 PSI or so when the pump is primed, and settles to a steady 35 PSI at idle. Pressure again raises to 42 PSI with the FPR vacuum hose disconnected, and drops as I apply vacuum to the FPR. Just another side note – Engine vacuum only varies between 19 and 19.5” Hg. (Does it make a difference if it was taken at the plenum?)

I don’t remember if I mentioned that this is not just a cold start issue. It’s all the time. Except for right after I shut the car off. It’ll start right back up at that point. As for the high idle, though, that happens all the time – even after an immediate restart.

About the fan problem... They don’t only come on erratically with the Diacom connected. It’s all the time. I can start the car first thing in the morning and either one fan, or two fans, or no fans come on. I’ve watched the car at idle several times (talk about wasting a perfectly good day) and again, there is no rhyme or reason to their turning on and off. Again, I now have the A/C pressure switch disconnected with no change.

I apologize again for the long reply. I do wanna you very much for the help, though. I really appreciate it. Do you have any other advice? - John '89 L98

 

Anybody have any ideas? Thanks. - John '89 L98

 

All right... Now with the Diacom hooked up, here's what I get. I have a constant LEAN condition with my BLOCK LEARN MULTIPLIER at 149 and my O2 reading below 350mv (mostly < 100mv).

I disconnected the O2 sensor, and Diacom reads between 350 - 550mv. That gives me the impression that the O2 sensor (less than 3 months old since I thought that was originally the problem) is good.

I disconnected the MAF to make sure it's not sending a wrong reading, and there's no change (except for AIR FLOW RATE).

IAC is set anywhere between 20 - 30 counts, fuel pressure is around 36PSI, and injector pulse width is 1.7 - 1.8ms.

What am I missing? It seems as if I have leaky injectors at startup, but then I have them running lean. What's the deal? - John '89 L98

 

Check to make sure your AIR diverter is not pumping air into the exhaust manifolds, once in closed loop (it is going into closed loop?) the AIR system shoudl divert the air to the cat, if it's pumping air into the exhaust manifolds, it'll lean out the reading that the O2 sees.

I don't recall my injector PW, but seem to think it was higher than 1.6-1.7 at idle...something like 2.0-2.1ms, but I may be mistaken.

Whole monitoring the O2 voltage with the MAF disconnected, does it increase and cross count normally then?

 

Mike, Diacom says the car was in CLOSED LOOP mode almost immediately today (weather was quite hot out today). It also says that the AIR SWITCH SOLENOID was off, while the AIE DIVERT SOLENOID was on. That means it's doing what it's supposed to do, right? Of course, how would I check to make sure?

As for what the O2 readings were when I disco'd the MAF, I don't remember, but I believe there wasn't much of a change. I'll record my trip to work tomorrow to get a bigger picture. I'll post the results.

I just wanna mention that the car did die out on me when I disconnected the MAF. Probably normal, but thought I'd mention it anyway.

Thanks for the replies so far. - John '89 L98

 

This is kinda goofy the more I read it...
I feel the inj PW is small, again, I'm going by memory. But the short PW (IMO) and low O2 reading would/should correspond.

Unplugging the MAF shouldn't let the engine die (assuming all other things are fine) so it seems as if the MAF is the only thing keeping it running.

Since the MAF has direct inout to fuel and spark control based on airflow and temp, I'd wonder about the CTS readng the ECM sees? Could it be reading too high of a temp and leaning the mixture at idle?

It may also be giving a false temp at start up when he inj PW is set for startup. Is the engine an '88 w/ Cold start valve, or '89 without? I think you mentioned it above as an '88, but your screen name would indicate it's an '89 where the CTS would be one of the constants on fuel at startup.

It sure seems as if the ECM is geeting some type of input from something, telling it to lean the mixture, I think you can disregard the AIR diverter as an issue, it could cause a lean reading, but the ECM would try to compensate.

What else is strange, is that when you disconnect the O2 sensor...when I disconnected mine the sensor reading in the ECM defaulted to 450mv, no fluctuation, I owudl think your's should do the same thing?

Monitor the CTS temp via Diacom and look for any sudden/abrupt changes.

 

Sorry it took me so long to get back to you… Here’s what I have. Yes, it may seem the PW is a little short. Apparently, at idle in park, the PW is anywhere between 1.6 and 1.9. At idle in drive, though, the PW is upped to around 2.6ms. While cruising at around 2000 RPM with a TPS voltage of around 1.5, I have a PW of about 7.5ms and an IAC count of 78. At 2000 RPM with TPS sitting at 1.2v, I get a 4.9ms PW reading.

The O2 readings are closer to “normal” after I replaced the 4 month old O2 sensor (it was reading a constant 1100mv and causing the car to run pretty crappy. I put a used O2 in there, and it works fine now.)

All the while, the CTS reads anywhere between 183 and 190. As a side note, I watched the CTS warm up from around 75 when I started it up this morning. The fans are still doing their goofy thing, but I’m gonna try to keep that separate. Oh, and I also put the MAT sensor back to its original position as it seems to have little to do with telling the ECM the temp of the incoming air. I guess it's more for the sake of EGR operation.

Here’s something I thought was a bit interesting. During a couple runs, Diacom showed that the EGR diagnostics switch was off while the EGR was being commanded by the ECM. Could that mean that the solenoid decided to stop working? I try replacing it this evening to see if it makes a difference tomorrow, but it still wouldn’t explain the hard start problem I have.

I’m quickly leaning toward the idea of a leaking injector. I tried pinching off both the fuel supply and return hoses (separately), and fuel pressure still leaked down at the same rate. When I previously had done the injector test on the injectors, I forgot about the cold start injector. (It’s an ’88 LB9) So, I tried it this weekend, and I got somewhat of a strange result. It single-pulsed fine, and was comparable to the other injector values. But, when I tried the multiple-pulse test, it didn’t fire at all. The 9th injector is the same as all the others, right? So it should have the same results. Anyway, I’m thinking that the 9th injector may very well be my leaky one. So, can I remove the 9th injector along with the line coming from the fuel rail, and cap it off for now? Is that possible? At least until I can see if it is indeed the problem.

One more thing about the IAC… On start up, Diacom reads a value of around 145 counts, and then it slowly drops from there. All the while, engine speed is always around 50-100 RPM above desired idle speed. I set minimum idle speed to 400 RPM, TPS to .54, and timing is still at 6 before.

Well, that’s it for now. Sorry it’s so long. Thanks ahead of time. - John ’89 L98

 

Or... What are the chances of me having either a bad ECM ground, or bad ECM? Any thoughts on this? - John '89 L98

 

Anybody?

 

John,

You can remove the CS injector and run an '89 EPROM in it...or you may not need to replace the EPROM at all, I've heard of some guys that have just removed it and left the riginal PROM in, and had no starting issues.

No, the CS Injector is not like the others, not sure of it should pulse the same though, my '89 doesn't have one. My spare TPI setup does, and if I recall, one side of the CSI has 12 volts on it, and he other side goes to the thermal swith in the front of the intake...when the thermal switch detects coolant is below a certain temp, it will ground the other side of the CSI and that allows fuel into the intake for cold starts. I'm not sure how long it opens the CSI nor at what temp.

You can try to just unplug the electrical connection to eliminate the swtci as the problem, but in order to eliminate the CSI, you'll have to pull it out and plug it. I've heard on this board that guys use a nickel and some sealant, then use the CSI mount without the valve in it.

IF I ever decide on what I'm going to do with the topend of my engine and I get it back together before we're both very old men, I'll be more than happy to scan it while running...been so long since I did it, I don't recall the values.

 

Well, here's a small update... The car runs extremely rough at idle just about every time I run it now. It will sometimes get better after getting on the highway for awhile, but not always. In fact, there are times when the car starts up with it's "normal" hard start, runs fine for 10 minutes or so, and then starts idling bad again.

Diacom shows the O2 reading to be 1100mv each time it happens. The O2 sensor will be giving good values, then all of a sudden - bam, it'll max out and run crappy. It doesn't run rough when throttle is about 1/3 or more, and there seems to be a definite point when it goes from running crappy and back-firing to running like a raped-ape. I have to accelerate hard off the line just to keep from jerking the car.

I wanna say it's not the O2 sensor since it did this before when I had the new sensor in. It's just been getting worse every day. I'm just about ready to pull the ECM and see if a new one will make things better. Any suggestions? Thanks. - John '89 L98

 

Anybody?

 

Hey John, just a thought, but why not take a look at the ECM grounds behind the heads? kinda tough to get to, but loosen the bolt and wiggle them in to try and make good contact.

Another thing too, after re-reading through your posts, you mentioned a gutted MAF, try unplugging it and see if it gets better.

 

On my way to work yesterday, I disco'd the MAF again, and the car still runs. Diacom shows the same maxed O2 value. I reconnected the MAF and disco'd the O2 sensor. Diacom showed no change. I shut the car off, restarted it, and instead of having the O2 value at around a constant 450mv as it should be, it was still maxed out. After around 10 minutes or so, it settled down to between 625 and 775mv.

The O2 sensor was still disconected on my way to work today, and Diacom showed almost identical results. Only this time, O2 readings would jump back up to 1100mv for awhile, and back down again.

So... I'm down to either a bad O2 sensor wire (going back to the ECM), or a bad ECM. Am I missing anything? Thanks again. - John '89 L98

 

I had the same problems as you, turned out it was the ecm. Car runs good after replacing it, hope this helps!

 

With the O2 disconnected, you should read 450mvs...this is the ECM's bias voltage. Unless there's some K factor in Diacom, I'd suspect you have an issue internally in the ECM.

 

Well, until I get a new ECM, I can't call it official, but I can say I pretty certain my present ECM is the culprit.

I pulled it out from under the dash with Diacom running (with O2 maxed out), and rapped on it a couple of times. Sure enough, it dropped to a dead-on 450mv. I re-connected the O2 sensor, and there it was, working as it should. The idle smoothed out, and I didn't have another problem with it until I almost got home. But it was quickly corrected with another hard rap.

I'll pick up a new one tomorrow, and that should be the end of that. Thanks to all who gave advice and suggestions. Now on to my fan problem, and hard starting issues... - John '89 L98

 

John,

Instead of replacing the ECM, have you inspected the edge connectors (from the engine wiring harnesses)? The solder trace "contacts" that are located on the card edges can deteriorate with age, humidity, and heat/cool cycles (thermal creep of the connectors).

You can try removing and reseating the connectors several times to help wipe the contacts clean. After all, they have been sitting there untouched for at least ten years. Replacing the ECM will do the same thing, but will also cost you a few bucks in hardware. Reinstalling your connectors is basically free, and probably worth a try since the inpact from tapping on the ECM case also rattles the connectors.

Just a thought.

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Later,
Vader
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"Get UP - Drop the bombshell!"
Adobe Acrobat Reader

 

No one else has jumped on it, so I will. That is WAY too much pressure lost WAY too quickly. You've got leaking injectors or (possibly) a bad fuel pressure regulator. The best way to test is of course to pinch/block the return line off. If the pressure still drops, guess where the fuel is going...

 

Vader, that was the first thing I tried. Call me cheap, but I also figured cleaning up the connectors and reconnecting them would be much more economical than replacing the entire ECM. Fortunately, there's a guy I work with in the National Guard who works part time at Auto Zone while he goes to school. That oughta get the price down a little bit.

99Hawk, I already tried pinching off the return line as well as the supply line (both individually, and then together), but with the same leak-down times. That's why I'm leaning toward a leaky injector or two. I just have to find time to pull the fuel rail and check for sure. - John '89 L98

 

Well, the new ECM seems to be doing great... I haven't returned the core yet, as I'm just waiting for a few days, but it seems that problem is solved. A huge thanks to all that replied. It's amazing how frustrating something like that can be. Oh well. On to my next problem... - John '89 L98

 

If you pinched off both lines and the pressure still dropped that quickly, you've definitely got a leaky injector. Hell, it almost sounds like a completely stuck open injector!

 

Well, I pulled the only injector that is easy to get to (cold start injector), and it's not the culprit. On to the rest of them. <sigh> Could there possibly be an easier way of checking than lifting the fuel rail up? - John '89 L98

 

Just to finish up on this post, I wanted to mention that the cause of my hard start problem ended of being a bad fuel pressure regulator. It was sucking fuel right into the plenum through the FPR vacuum hose. Go figure.

Anyway, I had a spare fuel rail complete with injectors and FPR, so I simply swapped it in. Seems to be working fine now. Now on to my "erratic fan" problem... Thanks to all who posted. - John '89 L98

 

Nevermind. Helps if I read the *whole* post.

 

John,

Thanks for posting back with the results. Most often the threads just disappear and everyone assumes that the problems were solved. I'm guessing you have been busy for the past couple of months. I know several other active and reserve people who have been as well.

I thought the last post about the ECM was the end to the problem - that's what I get for thinking again...

The FPR leak explains a lot of your starting and idling problems. The rogue O² sensor certainly didn't help, and I'm still confused about the EGR diagnostic data. The CTS seems completely normal, and TPS and MAF operation seem correct.

The fans are a different story, however. I know you have swapped relays and checked the A/C pressure switch and the auxilliary fan switch. The new ECM should eliminate that as a potential problem, since the car acted the same with both ECMs. About all that is left is the wiring, including relay sockets. Given some of your other strange readings, like the EGR sensor, I'd suggest starting with the ECM grounds on the engine. Clean and tight is a MUST for those grounds. You probably already realize that the control for most ECM loads (including the fans) is done by completing the ground path for the loads or relays, not the positive power circuit. Any stray or random grounding can really create havoc.

Inspect the relay sockets closely, and check the wiring inside the convoluted tubing for the fan controls. You might want to even open the relay cases and check for corrosion or carbon/copper flash. Short of digging into the ECM wiring harness, those are all the items I can think of off the top of my pointed head.