Coach Hawk

I searched here for weeks, and tried everything that was suggested, but still no luck. The car is an '88 Firebird, 2.8/auto trans, all stock, 210,000 miles. We were having issues with it even starting and running, but we're to the point where it will do that. However, it idles very rough, and seriously lacks performance. In neutral, throttle response sucks, and with the pedal to the floor, it will barley reach 5,000 RPMs. On the road, it barley goes 55, and the engine doesn't rev hiogh enough to shift at WOT, you have to let off the gas to get it to shift. It often dies when you put it in gear if your not on the gas a bit. It also pings severly at off idle. It likes to fowl out sparkplugs, and runs the same hot and cold. it acts kinda like it's running lean, but still fowls plugs.

Here's what we've looked at or replaced so far:
new plugs, wires, cap and rotor
ignition module tested
pickup coil tests ok with DVOM
cleaned IAC and throttle body
replaced coil
new O2 sensor
hollowed cat(cause we thought it might be plugged)
disconnected cold start valve
injectors tested for leaking and proper spray pattern
fuel pressure is good(45-50 PSI)
new fuel filter
new air filter
new MAF(it had a MAF code when we bought it, code's gone now)
new timing set
ignition timing is spot on(with ETC disconnected)
replaced all vacuum lines
EGR seems to be working properly

Is there anything I forgot? I'm at my whits end with this car. Next time my buddy buys a car that says "runs good" on the windshield in shoe polish, I'll make sure he doesn't have to trailer it home

Xophertony

seems like you have done everything. have you tested the compression? all i can think is that perhaps your cylindars are leaking all your hp out of some undetected hole???

have you replaced the idle air controller yet? next on the list might be computer.

and tell your buddy that a car that "runs well" does not need a trailer, they are usualy driveable. well once you are done fixing it for him it will run like a champ.

Coach Hawk

I cleaned the Idle air controler and related passages, it was pretty dirty, but was operating ok. Compression is at around 150 PSI on all cylinders.

Gumby

TPS

Gumby

Gotta be the TPS is bad or out of adjustment. If everyhing else is good and its your throttle response that sucks. It out of wack makes sense..

Maybe also test your ATS

TPS throttle position sensor
ATS air temp sensor


How new are the plugs and wires?

Sure your coil is good?

camaro_junkie

It's a stupid thing to check, but make sure the spark plug wires are connected in the right order.

Gumby

If all that checks out. I would check the computer. Make sure it has the right computer in it and chip. Then see if you can give a junk yard $10 to test one of their computers in your car.

Fast355

iTrader: (2)

Whats the fuel pressure under load? If for example you had a plugged strainer in the tank, you can get plenty of pressure at idle, step on the gas, the system now needs volume it can't produce, and the pressure sinks like the Titanic. That would explain the lack of power, ping, and rough running.

Also if the balancer has slipped(my original 2.8 Jimmy engine did it which ultimately knocked a hole in the piston) it will let you advance the timing by that much and still read 0. If it were my car, I would also try to pull about 5-10* of timing out of it and see where that gets you. Runs better, pull a little more, until it falls off, then move it back to where it runs the best.

xplane

i would say the computer my car was doing the same no power/ wont accelerate even at normal highway speeds put in a good computer and it runs great. have you run the car with the battery unpluged or bad? thats what F'ed mine up. oh and use a vacule gauge to test the amout of vacume mine had a line that when i put it on the edge curled a little bit and it would not idle worth crap till i found that. i dont know if this will help ya but mine was doing the exact same stuff and thats how i fixed it

2_point8_boy

The computer is the LAST thing that you check.

How did you test the EGR?

Disconnecting the Cold Start Valve could have something to do with the cold idle quality, Plug it back in, it's there for a reason.

Just because the ICM tested ok, it could still be crap...as a mechanic, I've seen plenty of them like this...including my own, twice.

How did you test the injectors, removed from the vehicle?

Definitly sounds like you have a fuel delivery problem from all the symptoms you described. Have you looked at the CTS(Coolant Temp. Sensor?)

Also, when the car is running, ground the ALDL and see if it's blinking slowly. If it blinks fast all the time, then you are stuck in open loop and there are 3 things that need to happen to go closed loop, The CTS must be abouve a certain temp, the car must be running for a certain length of time, and the O2 sensor must be responding.

The CTS temp is the most important thing in there, so if it's bad, you'll get a good quick idea from the ALDL test. The CTS has EVERYTHING to do with pulse width, so it's important that it's working properly.

Was the distributor ever removed from the vehicle?

bobdole369

I'll second that..... I almost took the head off, then by luck my friend came by and immediately found I had 2 plug wires swapped. Just cuz you put em back on where you took em off doesn't mean its right, specially if your not totally familiar with it.


Did you run it without any of the exhaust when you did that? (ie out of the y pipe?) still could have a clogged muffler. Most of my cat ended up IN my muffler when my cat plugged.

PCV valve (and its tubing!) can cause pretty bad running, but you said you did the vacuum lines, so I'm assuming you replaced that as well.

It's OK to run without the MAF plugged in. It'll put the car into "open loop mode", and it'll take the aforementioned sensors out. Its a good diagnostic at the very least.

Any other codes?

V6sucker

ok, you have some probs listed that are caused by the same thing.
You need to check your fuel.
I will also bet that you are burning up the rings. Why?
the low compression, and the constant cranking/no start while fuel washing the cylinders stripping away the lubricant oil.
So, first thing you should do is... pull the dipstick and sniff the oil. I bet it wreaks of fuel so it needs to be changed.

Next, pull upper/middle intake. Pull the fuel rail, remove the feed/return fitting. Get a line and try to blow through the return side. If you can without TOO MUCH trouble you should be ok.

Then check the distributor. You need to see it has been removed and installed out of time. Remove plugs, turn to TDC and verify #1 position. Remember that #1 plug/wire is passanger front. If that checks out, reinstall the wires plugs in correct order.

Then move on to the TPS, whiop out the volt meter and a tech book. It has the precedure laid out so I will not go into it, just follow it.

You may want to verify that the EGR is fully closing. It can do really strange things if it is not.

KED85

I AGREE IT'S CLOGGED MUFFLER DUE TO THE CC STUFF BLOCKING THE ENGINE EXHAUST FLOW!!!
Simple drop muffler. IF NOT BAD, reweld up & be on way, $30 lighter in wallet.
Then keep trying other suggestions.
Your muffler is so clogged due to the bad/old CC!

KED85

I AGREE IT'S CLOGGED MUFFLER DUE TO THE CC STUFF BLOCKING THE ENGINE EXHAUST FLOW!!!
Simple drop muffler. IF NOT BAD, reweld up & be on way, $30 lighter in wallet.
Then keep trying other suggestions.
Your muffler is so clogged due to the bad/old CC!

Coach Hawk

Ok, I finally had some tiime to do some more testing. We're back to starting ok, and idling smoother, but still seriously lacking power. Like not enough power to drive safley. Still fouling plugs too, so it seems like it's rich, but it knocks at low RPM when you snap it open.

For starters, the muffler is NOT plugged. It does not run any better with the rest of the exhaust disconnected.
No new codes yet.
The TPS checks out ok, .5V closed, 4.3V wide open.
The oil does NOT smell like gas, so i'm not getting much, if any, fuel into the crankcase.
Under load, the fuel pressure RISES instead of drops, and peaks around 50 PSI.
Manifold vacuum at idle hovers around 10 in/HG
The distributer has not been out before, it's lined up where it should be.
Plug wires and firing order were double and tripple checked.
PCV double checked and in proper working condition.
Computer and PROM are verified stock and correct to the car
Injectors were checked by pulling the fuel rail and watching them spray, and checking for leakage.
CTS seems to be working correctly, but I'll double check when I get a chance.
EGR was unscientifically checked by pushing the diaphram while it was running, where it promptly started sputtering. I can't get the bolts loose to take the EGR off the exhaust manifold, so I can't clean it out any.

With the ALDL jumped, I get a constand flashing, hot or cold, about 3-4 flashes a second. So I'm stuck in open loop? What would cause that? If it always runs in open loop before it warms up, why does performance suck so bad? I can't imaging it always ran this crappy when it's cold.

Also, there seem to be two coolent temp sensors right next to each other, one with a standard 2 wire weatherpac plug, and one with a plug like a fuel injector. I think they work because the resistance changes as they get hot. Why are there two, and what are the specs for testing them? Thanks.

bobdole369

MAF or MAP system also needs to be operational for it to enter closed loop mode. As for that, Firebirds are in open loop mode until the O2 sensor heats up, the CTS heats up, and it has to have been running for a period of time. So when you first start it, it IS in open loop for about 1-10 minutes. It should still run OK even if it is in open loop mode. I'm personally too cheap (and I kinda like the way it runs) to replace my failed MAF, so I run open loop just fine all the time with the MAF unplugged.

CTS is very important, but then again it doesn't seem to matter in open loop (i.e. when you first start the car, when you are having this problem), as you are using fixed values at that point, so while something to look into, that isn't crucial.

I think thats enough to establish it isn't leaking badly enough to affect the engine, as it would have not changed much at all had it been leaking.

Is it possible it was installed 180 out? Or perhaps the previous owner had done that and you followed his lead? or was it obviously the original?

You have good vacuum, compression, spark, and (apparently) fuel. Grounded spark plug wire? One other thing could be to put a spark tester inline with each wire in turn. (Yep, I saw how you already replaced the most of the ignition system.) How bout just replacing the ignition module despite it testing good? I don't think theres a condensor on that one. You did put grease under the module right? (having that metal bit on the module ground out causes problems, also the grease is supposed to help alleviate heat to the module) Being a very hot area, the connectors leading to the module are very brittle and may be intermittent. This is a problem area, consider replacing them.

putzing with the timing a few degrees forward and back won't hurt too much, might tell you something. especially since you just pulled the balancer to do the timing set.

Missing anything else external guys? a valve problem would show up in the compression test, which was OK, same with heads. Seems we have fuel and spark too, what gives?

Coach Hawk

I did fiddle with the timing some, forward and back to the points where it was barley running. the low RPM knock never went away, and it seemed to run best where it is supposed to be.

The plastic part of the plug connecting the pickup coil to the module is long gone, so the connectors are just slid onto the prongs. The pickup coil looks origional, the moduel was replaced once upon a time. But if the pickup coil was bad, wouldnt it either work or not work? It did test out ok with my DVOM.

Also, I don't know if it's related or not, but I just remembered that the fan acts funny. Key on, engine off, the fan kicks on. As soon as you crank and the engine starts, the fan kicks off till 220* or so like it's supposed to.

Gumby

Well the car stays in loop mode until it gets a good signal from the O2 sensor. Why newer cars run a 3 wire so its pre heated and works right away.

Worthy mod for any 2 wire car.

Maybe check your ground straps.

KED85

Coil replacement & new connections.
Still check muffler
My clogged muffler had no true drivability issues.
Until I pulled it I never would have believed it.
The Muffler side exits pipes had become loosened, which was cause for muffler shop visit & muffler removal.

TomP

Wow, great "test" list!! That eliminates a lot of guessing!

Originally, you said the engine wouldn't rev up to 5000 in neutral. Does it rev that high now? Or does it still sputter out?

Three things I can think of:

1. Was the spark coil replaced yet? If it was, could it be bad?

2. Bring #1 up to TDC/compression and make sure the timing mark on the balancer lines up with 0 degrees on the timing scale.

3. Have you run the car with the MAF unhooked yet?

Coach Hawk

The old coil was arcing to the valve cover causing an intermittent miss, so I replaced it with a known good coil. The miss went away, but is still doesn't perform any better.
Timing mark on the damper is verified to be at 0* with #1@TDC
It still won'r rev up to 5,000. It doesn't spitter or misfire at high RPMs, it revs up smoothly, but slowley, it just lacks the performance to rev that high like it's being choked but the intake and exhaust are both clear.
The MAF was replaced already because at first, we had a MAF code. Now, if I unhook it, it throws tha MAF code but doesn't seem to run any differently. I'll verify that again today.

Thanks for all the help and suggestions, I know we'll get this thing nailed down soon.

2_point8_boy

There's you're problem.

at idle you should see about 16-18 in/HG.

Have you adjusted the valves recently?

Is it a steady reading or does it fluctuate?

When you snap the throttle open, does it go down to 0?

If it does, what is the reading after you let it rev up and then let it snap closed?

Gumby

That would depend on his timing too.
I vac time my V8 to pull 17-19 at idle.


Almost wonder if he is 180 out. Buddy had a VW that just would never run very well. Sold it and the guy said it was 180 out, then drove it all over the US.

KED85

On our V6s
If ya off on timing (including 180* dist outta phaae), it won't start or run at all
IF plug wires screwed up it won't start nor run at all.

Coach Hawk

Ok, so...
KED85 is right, it will not run at all 180* out. I tried just for good measure.

I swapped in a new computer($40 bucks used!!). it idles a bit smoother, but performance still sucks.

I verified that the CTS is working properly.

I rechecked the vacuum.
It idles at 10 In/HG nice and steady, when you open the throttle, it drops to 0, then jumps to 17-18 when the throttle is closed and drops back down to 10 as the RPMs drop.

It still knocks and almost dies when you try and put it in gear. Any more ideas? Your input is greatly appreciated.

2_point8_boy

have you done valves or anything recently? I already asked, but never got an answer.

With low vacuum like that the first thing I would look for is vacuum leaks. You said you already checked for them, but there were none, but how did you check?

With the list that you have given of all the stuff that checks out alright, the car should be running perfectly, but it's not, so unfortunatly I have to assume that something on the list has either not been checked, or checked wrong.

I would address the low vacuum problem, then once that's taken care of, you should see a HUGE gain in performance over 10 inches.

How fast does the needle return to 10 after you snap accelerate?

Coach Hawk

Well, thanks for all the info. I've tried absolutly everything you've suggested, and it's still no better so I quit. I'm swapping an LT1 into my '91, so I'm going to swap my 305 TBI and associated stuff into this car.

Gumby

Sometimes and engine just gets tired.
Are you gonna part out the 2.8?

Xophertony

good luck with your swap

True_bird

Wait dont give up yet....there is one simple thing that I am fairly sure noone has suggested yet, does the car have cruse control? if so unplug the vacuum hose that goes to it at the back of the intake manifold by the disributer cap thats what my problem was with my 2.8 it had no power and was VERY sluggish to the point of dieing I disconnected the cruise and now its got its ***** back!

Coach Hawk

Sorry True-bird, the cruise was one of the first things disconnected, and the fitting capped. Good suggestion though. Only thing left I can figure is a vacuum leak UNDER the intake from a bad intake gasket or cracked manifold or head. I'm to the point where anything else is just throwing parts at it on the hope that it'll run better, not to mention I'll have a prefectly good 305 and trans for it in a few short weeks.

Gumby

Have you run the car in the dark to look for spark leak?

Coach Hawk

I have already checked the sparkplugs. I replaced the coil already

Gumby

Don't matter, went through 3 new coils once chasing down spark leak.

only in the dark could I see it.

Coach Hawk

Sorry, what i ment to say was that i checked for spark leaks already, and found one, which is why i replaced the coil.

Gumby

Well check it again.

I started with an accell coil, then went through 3 oem coils. Kept trading them in, got stuck with 1 for a spare.

Problem wasn't the coil but new one would quickly start to leaky after jus a short bit of use. But took some time to catch on as I kept finding yet another brand new coil spark leaking like a BI... for no good reason.
Ended up putting the original coil back on in the end.
Once the true problem was fixed.

[treu problem??? was never found, an early full tune up made it go away, faulty plugs or wires I guess. Who knows]

Coach Hawk

I've checked, double checked, and re-checked. There is no spark leak anywhere. This motor is cursed. I'm going to pull it out, throw a party, and toss it in the fire. We'll dance around it and rejoice...

KissThis

The exhuast is the first thing I thought of. When you dropped it where did you drop it from?

Try dropping it directly from the manifold/Headers.

This has been a funny little problem in a lot of the cars I help fix. the Cat converter will get clogged and pfft.. nothing.. if you don't want to drop it you can grab yourself a rag of some sort and place the rag and your hand over the exhaust pipe. Have someone start the car. A good system will push your hand away.

But, again it depends on where you dropped it from the first time. At the headers, then ignore me, further back just try it again. What's it gonna cost you? a couple minutes to try the tail pipe trick.

Who knows.