Overcome90

My car has given me a world of trouble since day one. Basically, whats happening now is the car starts great, idles smooth, stays cool, and revs strong. It is a 5 speed. However, when I am driving down the road, if I try and give it a lil extra gas or "get into it", it jerks and loses power, followed by the check engine light. After the light is on, it has significant power loss, I can smell gas, and the exhaust will kinda rumble and pop(as if i had headers and nothin else haha). I have replaced ALOT. I have replaced the coil, the distributor cap/rotor button, the pickup/coil thats in the distributor(one that requires removal and disassembly of distributor), the EGR valve, the heater control valve, a new fuel filter last week(third one in bout a year), plugs, wires, air filter, catalytic converter is gutted, smog (AIR) system removed-thanks to awesome article plus a little research from this very site!- and im sure there's more that I will remember once the questions and opinions start coming. My current guess is the MAP sensor?...what else could it be? I have had mild engine work done(1 above stock cam, heads shaved, I drilled out my injectors a bit, exhaust, open element..somethin else too) I had a fuel pressure check done, the mechanic said pressure was low but he never told me where he checked it in fuel system. All I remember is he said "key off, key on psi is 37, should be 45". SORRY for long post, any ideas?????

travis401

iTrader: (1)

try un plugging the ESC module and take it for a drive. if it does the same thing, replace the ESC module.

Overcome90

is that the knock sensor? I have replaced that, as well lol. Told ya I'd start remembering

Overcome90

ohhhh the module!! I never thought of that, my bad thanks

travis401

iTrader: (1)

yea, the ESC, (electronic spark control) module should be bolted to the cowl lip on the passanger side. if it goes bad, the car doesnt advance or retard the timing based in the demands of the engine. itll idle fine, but start spitting and sputtering when you mash the go pedal, and possibly throw a code for the lean or rich condition. (in your case sounds like a rich condition.)

Overcome90

Well, I unplugged as you said. I had a rough idle from the go, and a major loss of power, as well. It threw the code before I put it in gear, and even in neutral it was sluggish climbing the "R's". Im not sure how to diagnose whether it was bad or not, since it was bad before I left the driveway. I drove it, it ran like sh**...haha. When I got back, I plugged it back up, it idled a bit smoother and had a bit more power. After all of that, I decided to try diagnosing the MAP sensor via a thread I had found on this site. "RFMaster" had posted a few things. He posted that with key on and engine off the MAP voltage(pin B/light green wire) should read around 4.8 to 4.9 volts. Well, mine read(with a multimeter) around .8 or .08 dont quite remember now. What I DO remember, is that reading was exactly the same as pin C(for mine was a purple wire). He stated that if this instance is true, then the MAP is probably bad. IS this true? Also, I have vacuum at the sensor. Any other help guys?????

travis401

iTrader: (1)

if it ran worse the the esc disconnected, then its working right. as far as the MAP, i have no idea on that one.

Overcome90

cool well thanks alot because that was something I had not thought of and I was hoping you were right because the bracket wasn't even mounted haha. But.. guess it is workin. If anyone else has any suggestions, please feel free to let me hear them haha. You can be rude if ya want, so long as its good advice

Overcome90

anyone?

Overcome90

well tomorrow I am going to try to find a MAP sensor from a junkyard or somethin just for kicks... is it possible that my fuel pump is weak and causing this?? I know there are very knowledgeable members on this site..plzzz helpp!!! Thank you

travis401

iTrader: (1)

when was the last time you changed your fuel filter?

Overcome90

last week..and its only been started half a dozen times since because I had someone run into the back of me and messed up my new paint job so I have been prepping my new freakin body kit for repaint :/ I originally was going to drop the tank that day but decided to just change the filter and also replaced the rear sway bar linkage too and didnt feel like it. I am pretty fed up with the car and the engine at this point. 2 years of replacing **** on a fixed budget(full time work + school + family)

Overcome90

i got a compression gauge and went to auto zone and got a loaner hand pump vacuum gauge so I am going to fully test the MAP sensor in the am and run a compression check on all cylinders. At this point, I dont even want to spend the $50 on ANOTHER diagnostic check with my mechanic. Im surprised no one has any advice

UNCLE TOM

iTrader: (1)

have you ckd. fuel press. . fuel pump can be working fine but not putting out the press. . the fuel pump connects to hard lines with about a 2in. section of rubber hose . this small section of hose can deteriorate and leak like a sieve . old age and maybe ethanol eats up the rubber hose . its a PITA to change (you might as well install new pump at the same time) . just my thoughts , good luck .

Overcome90

I have had the fuel pressure checked but it was by a mechanic who still has not returned my calls(months ago). How can i check it myself? Does the tank have to be dropped in order to have access to this section of hose? I am trying to make that a last resort considering how I will have to do it in gravel with limited tools. Just cannot afford to have someone else do it for me. Thanks. Also, is it possible it is the fuel vapor canister causing this?

Overcome90

Attempted to do a compression check today, but the enigine compartment is so TIGHT i cant even get it screwed in to the number 1 cylinder. I have a haynes manual for this car, which is NO help!. Took me 20 minutes to find the fuel pump relay, which was mounted on the firewall to the same bracket as the freakin esc module!! My fuse box has NO f pump fuse(as shown in haynes manual). Aggravating stuff man, these cars are terribly cheaply designed. Any advice on getting a compression gauge to fit????

Overcome90

I have also found a thread on this site that talks about scanning codes with a paper clip. I am DESPERATE to try it. Tried to find my connector that a obd1 scanner WOULD connect to, but it isnt mounted as shown in haynes manual, and I dont know how to recognize it if I even looked at it. Under my dash i just have a bunch of wires and connectors everywhere. Maybe Ill take some pictures If I can squeeze in. ANY HELP FROM ANYONE WOULD BE APPRECIATED PLEASE

UNCLE TOM

iTrader: (1)

on 90,91,& 92 the OBD connecter is just to the rt. of the fuse panel . not as easy to get to as 89 & below it's a flat 2 row female connector. on the rubber hose , yes the fuel tank must be accessed . thats why i mentioned it's a PITA . fuel tank must be dropped or access panel cut . (i cut access panel on my last fuel pump change) don't fret over comp. ck. yet , get it running first . do a search on fuel pump change & access panel , you will find MANY how-to articles . don't get frustrated and tear stuff apart , research before you jump into a job . members here have done it all , don't be afraid to ask . (the only stupid/dumb question is the one not asked) good luck .

Overcome90

thank you bud ill keep ya'll posted

RBob

iTrader: (1)

First thing to do is to throw the haynes manual away.

Second, find a new mechanic. TBI fuel pressure is 9 to 13 psi, not the 37/43 psi that MPFI runs. Appears that he didn't even check it?

Third, to check the fuel pressure need to add a tap to the feed line. As factory stock there isn't a test port. It is possible that the fuel pressure is low, as this will cause a loss of power under load.

Fourth, The electronic spark control (ESC) is the knock detection & reporting system. It is the job of the electric spark timing (EST) system to control the spark advance via the ICM.

And finally, odds are the ECM is tossing code 43 (ESC malfunction). The ECM does a forced knock test that is probably failing. When it does code 43 is set and a set amount of spark advance is pulled. This is what causes the loss of power. And remains until key-off.

Since the engine has been modified the ECM can't get it to knock during the forced knock test. So need to either advance the timing a bit or use a lower octane fuel to get it to knock during the test.

Note that there are several threads on the TBI board here concerning the forced knock test.

With the modifications you need to get into tuning the calibration in the ECM. This is the only way you will have an engine that runs correctly.

Interested in how the injector spray pattern is after drilling them out.

RBob.

Overcome90

thank you so much for the extremely informative reply!!! I have a question about code 43. If the car is in neutral, I can give it all the heavy throttle it can handle. It only does it under heavy throttle while in gear(under load). Does this mean anything significant? Thank You

RBob

iTrader: (1)

There is a minimum MAP (load) parameter that needs to be met. It could pass the forced knock test by rev'ing the engine in neutral. But as the engine gains RPM the load is reduced. So there is a very short window of opportunity.

RBob.

Overcome90

ohhhh I see. Another question, are my injectors supposed to drip fuel at idle? I was playing around with the sensors and double checking my wires, as well. I would let it run and pull each sensor to see how it would affect it. When I pulled the connector from the egr vacuum solenoid, nothing happened. I pulled the vacuum line off of the EGR valve and did not feel any pressure (blowing or sucking). So I decided to take a thin screwdriver and push up on the diaphragm, it definitely lowered the rpms, almost killing the engine. Could I have a bad EGR vacuum solenoid? It would have to be ordered and arrive Tuesday. Could this be the cause of everything? or do I just have multiple issues at once, haha. I hope I am not a bother, thanks for everything. -side note, the mounting bolt for the solenoid was in the intake, and it smelled and looked like old burnt gas or something.

Overcome90

I tried messing with the timing by loosening and turning the distributor, just listening by ear. I could turn it pretty far and it didnt seem to affect anything. In my haynes manual, which yes I know is trash-worthy lol, it says I have to disconnect the est bypass connector to change initial base timing. The picture it provides is pretty indistinguishable lol. Can I just check the pressure at the fuel filter?

RBob

iTrader: (1)

To check/set the base timing via a timing light, the EST/BYPASS connector needs to be open. Stock for an L03 is 0* (at TDC).

You can check the fuel pressure at the filter. Although I wouldn't, as you will be under the car tapping into the line while it is pouring fuel out. If you do it there be sure it is on the outlet of the filter. Which, IIRC, is the fitting toward the inside of the car.

Much easier to do it under the hood at the line where it goes from the frame to the line on the intake manifold. The larger of the two is the feed to the TBI unit.

RBob.

Overcome90

found connector...disconnected and reset timing. Seemed to help the miss at idle, but I am STILL getting code 43 under heavy acceleration. I set the timing to 6*. How can I check for an "open circuit" like the haynes manual describes. Could it be that the knock sensor I replaced is a bad replacement? I cannot afford to throw parts the problem any longer. I really dont feel like running a lower octane gas would magically fix the problem. There has to be a way to determine WTF is wrong

UNCLE TOM

iTrader: (1)

YOU HAVE STILL NOT CKD. FUEL PRESS. . seems like you are stabbing at everything except the obvious . check the DAMN fuel pressure .

Overcome90

WHY IN THE **** WOULD LOW FUEL PRESSURE THROW A CODE 43????????

RBob

iTrader: (1)

To test the ESC system:

Bring engine up to operating temperature.

Hold the engine RPM at 1200 - 1400 RPM.

Rap on block with a wooden stick (handle of hammer, broom handle, etc).

Engine RPM should dip down as the ECM pulls spark advance. Then recover as the SA returns.

> I really dont feel like running a lower octane gas would magically fix the problem.

Not sure if you don't want to run a lower octane fuel, or that doing so won't fix the issue.

During the WOT forced knock the ECM has to see knock, period. If it does then all is OK, and the ECM will then also add the PE SA during WOT.

If the forced knock test fails, then a set amount of SA is pulled (loss of power), and code 43 is set.

Believe me, the first time an ECM attempted the forced knock test on a modified engine was an eye-opener. A burst of power, knocking like crazy, and I lifted as fast as I could.

Later that day the test was disabled. A bit later it was removed from the code (the ECM's firmware).

Note that you aren't the only one to have this issue. I've released patches for the '7747 ECM and the early '8746 ECM code to set the flag that the test passed. Which does two things: the ECM thinking the test passed won't run it. And the ECM thinking the test passed will have PE SA added during WOT.

RBob.

UNCLE TOM

iTrader: (1)

ck. your own posts # 1 ,10 , 15 . i'm done .

Overcome90

Seriously?? You can count but you cant read apparently. The most recent posts indicate that I have diagnosed the SES light/code to a code 43. Sure, the FP could be low, but is that throwing the code? NO! Is that causing it to sputter and miss and cut off? NO! So, by your own advice, I think I will "get it running right, first". Oh and thanks for the info about chopping a hole in my car...Ill definitely look into that.... Idiot.

Overcome90

Yeah I follow ya. I bet you get tired of explaining this over and over( I read all the other threads I could find btw). Its like 32 bucks for another knock sensor so I would rather know whether its bad or not haha. It sounds like the best way to go would be to buy an ALDL cable and that free software winaldl. But..at the same time, I am leavin for military duty and will be gone for 6 months. I just wanted the damn car to run good for ONCE before I have to go. The tuning/burning of chips investment seems stupid to me because I would never go all out on a smoggy 305 lol. Im at a complete loss. I am out of ideas. Ill test the knock sensor. I ran 87 octane for a couple days-did nothing but made it sluggish lol. Still gettin code. Im not too excited about getting into the wiring of my computer to attach a push button or tie in a resistor. I understand what is happening, I just dont know why. Thanks for your help
:edit: can I apply the patch to the stock ecm/prom/whatever or do i have to burn a new one? I would rather apply patch if it can be done to what I already have(naturally haha) thanks I await your reply

RBob

iTrader: (1)

Need to burn a PROM to apply the patch.

I was just looking through the code. Can try something, let the engine run at least 5 minutes, this can be at idle.

Then do the knock test outlined above. If it passes do it several more times. You are trying to get more then 2 knocks counts at once.

Then drive it and check WOT. If the above rapping on the block created enough counts the forced knock test won't be run. As the ECM has seen enough knock for it to be OK.

Note that if the wiring between the ECM and the knock filter is bad code 43 will get set from run-away knock counts. This will occur about 3 to 4 minutes after the engine is started. Can see this by unplugging the knock filter.

RBob.

Overcome90

Well I have had a chance to do some more diagnosing. I tried testing by letting car warm up and rapping on block. I did it with it at idle and I also did it with rpms around 12-1400. I didnt see or hear any change. I also found a thread with some excerpts from a GM service manual. I tested some of the connections at the esc but others require you to watch how applying voltage/ground affects the knock counts via "scan". Does this mean I need a scanner that has a knock signal function? Can I do this test using an ALDL cable and winaldl? I have had some health issues come up and I have another doctors appt in an hour but I also plan on following the connections to the ECM(i think its the black '495'? and another not sure?) does anyone have any advice on how to do that? Thanks

ninetyone

iTrader: (2)

fuel pressure is not checked with engine off. You also have a tbi car right? The average fuel pressure for this systems is between 12 psi, and no more than 15 psi.

ninetyone

iTrader: (2)

You know u need to disconnect the neg. battery cable for a few min. to clear any codes. Could be your connector that plugs into the knock sensor. I had one that kept coming loose.

ninetyone

iTrader: (2)

You may wanna check with other members,but IIRC ,you may be able to run a new wire from your knock sensor directly to your ecm. On your ecm it is b7. I would try that to eliminate a bad wire/ connection.