Hey guys, I have searched the forums and can't anyone else with this issue.

When I start the car I have to give it gas and keep pumping it until it starts. When it starts it sputters and acts like it wants to die. If I keep my foot on the gas and the temp reached around 125 degrees you can feel a kick in the engine and then I can take my foot off the gas and it runs like a champ. Driving it everything is normal. Has lots of pick up and not stalling with a smooth idle.

I have replaced the IAC, Checked all vacuum lines, replaced the fuel pump, fuel injectors, MAF, MAF power, MAF relay, TPS sensor, O2 sensor, new plugs and wires, distributor cap and rotor, Ignition coil and some other chip under the rotor in the distributor.

Going crazy over here... Any thoughts or am I over looking something?

Thanks!

 

Check the coolant temperature sensor on the front of the intake manifold. Look at the connector pins for corrosion and make sure the wiring is OK.

 

and make sure it is full of coolant and burped.

 

Awesome, thank you! I will do put a new one in today if this rain hold off. The wiring for it was just redone so I hope the part will take care of the problem. I will let you guys know what happens

 

I put the new part in and it cranks a little easier but still having to hold my foot on the gas before the engine kicks in and stays idle.

Any other thoughts? Could the cold crank injector be causing it?

 

Before we keep throwing parts, aka money at it, do yourself a favor and put a scanner on it. I don't have a MAF unit so I don't know what it should read but someone will be able to give you the plausible readings you should be getting.

Scanner will tell you what the ECM sees as the start up temp along with TPS. That will aid diagnosis.

What is the fuel pressure? When running, take the hose off and see whether it hits about 43.5, give or take. Do a WOT run and see if it holds pressure or drops down all the way. Check the spark quality and see if it is weak or you get solid blue flame

Injectors, where did you get them? Were they tested? What about the cold start? Did you have that one tested too?

 

did you look at your throttle body might need a good cleaning.

 

Yea, I have thrown a lot of parts into it but everything was original and has been running better since I have. I figured a car this old it would have to happen sooner or later

Crap really hit the fan when I put the injectors in. I got them off amazon and they are the Accel ones, 26lbs. It's holding fuel pressure but it's holding around 36 when the car is cranked and stays pretty steady.

I have a cheap code scanner but it gives me 11 codes and no matter how many times I fix what it's saying it still shows up. The check engine light however is not on when the car is running. I guess I need to go somewhere with a legit awesome scanner?!

How do I check the spark quality and the cold start?

Throttle body was cleaned out really well when I took everything off for the injectors.

Like I said once the car hits the 120- 126 degree mark it runs like a champ with no worry of stalling, just a slightly high idle.

I have never worked on cars in my life, so this is all new to me. Sorry for all the questions if some are stupid, haha!

 

Just saying that throwing parts to make a car run well without proper diagnostics is just flushing money down the toilet.

I'm not totally sold on the Accel fuel injector quality. Some have said they were OK, others no. Yes, I am aware that sometimes parts are made "at the same factory as OEM" but that doesn't tell me if the QC is the same as OEM. Wish you got some Bosch injectors. If it hit the fan when you did the injector swap, I am going to say that that is the first place I would look. BTW, I think those are larger than stock? IIRC, they are 22 or 24?

I suspect what you have is a code reader. That means you should have bought a box of paper clips from Office Depot because that is all it will give you. Not sure what code 11 is. Should it be 12 if there are no check engine lights? What you need is a scanner to interrogate the ECM. Get one that can read OBD1, test it and make sure it can.

Dark garage and engine running. Take a plug off (obviously it will run rough. Insert plug into a known good spark plug or a spark plug tested which has a clip to ground the threads. If you get a blue flame and rhythmic pulses, life is good.

Did you remove the IAC and the IAC housing? Clean all the passages with brake cleaner, use new gaskets? Also buy yourself a few cans of brake cleaner and spray all the hose joints when running. RPM goes up, you have a leak. After that, you will need a scanner to reset the IAC and then the TPS.

Who knows. Maybe the conditions at that point are right for an easy start? High idle? How did you determine that? The tach is not really accurate so you will need an inductive timing light with tach or a scanner to see what the RPM is as seen by the ECM.

Ask what you feel is a stupid question. It is cheaper than making a stupid mistake. Even if we laugh at you, the wallet stays just as fat. Making the stupid mistake puts the wallet in cash-suction mode. THAT HURTS. Trust me.

 

Yea my wallet has been feeling it. I took it to the corvette repair place here in Atlanta and spent $1,300 and it broke down on me 3 times on the way home. I do things myself and it starts working again. I'm just frustrated.

When I said 11 code, I meant 11 different codes. Here are the ones in this order. 34,26,25,24,51,45,44,43,41,63,54

Thought the accel 29 injectors were going to be good even though they were higher than what it was supposed to be. Everywhere I read said the 29lbs really made the car run awesome.

AS far as high idle, I was going off the dash. When I checked with a spark reader. When I got the spark to where it should be the car died...

I have not cleaned the IAC housing. I sprayed everywhere with carb cleaner and nothing jumped.

So i should have reset the computer after I put the new IAC and TPS sensor on? Does that go for all other parts and relays? Did I need to reset anything after I installed the injectors. I just plugged and played, was that wrong?

 

I have used HiTech in MN or LPE in Decatur, IN and had good luck with them.

I'm going to say get a scanner to clear out all the codes so we know exactly what we are dealing with. That or power down the car and disconnect the battery for a while. Recheck after running for a while and getting codes.

If the stock is 22 or 24, 29 will not make it run well. Just dumps a lot of fuel whether it needs it or not. Whether the ECM can adjust and how well is another story. Your ECM is set up for 22 or 24. More is not better. I have 42pph injectors but my ECM is programmed for it. Put them on your car and I'll be surprised if it runs without flooding.

Dash tach is not accurate sometimes. Mine is after I got it adjusted but previously it read 300-400 high. I'm not following. How did the spark reader get the spark where it should be?

The IAC housing is where it can clog up and restrict air flow. Basically the IAC is a "metered air leak". So if the ECM says it needs 30 counts and it still needs more air, it sends more counts. Not sure I am explaining it well. I would take the TB off, remove the IAC housing and clean the passages and GENTLY spray brake cleaner on the pintle and GENTLY wipe. New gasket and reinstall.

I always reset the IAC. I don't like the way the FSM does because it caters only to 100% stock. Anything else and there are no guarantees. I reset it with a scanner. Engine running with everything else off, I see what the IAC counts are. Target is about 20-30. After that, I set the TPS to 0.54V. This is all assuming you have the timing spot on and that the harmonic balancer is not walking around giving you inaccurate readings. As to the other sensors, no you don't have to reset the ECM. All you can do is wipe out the old learned data. Without re-writing the chip, you really can't do much. That goes true for the injectors. The ECM is programmed with stock size and you can put in my 42pph injectors but it won't know. It will try to adjust but there is only so much it can do.

IIRC, the fuel spec is 43.5 psi. That is where the rating should be at. SO I would say my injectors are rated at 42pph at 43.5psi. Change the fuel pressure, you change the volume. So at 50psi, the injectors might be dumping fuel like a 50pph injector would at 43.5psi.

http://www.fuelinjectorconnection.co...tor/index.html

A quick review shows it to be 22pph. So 24 might be ok. 29, probably not

 

Did you disconnect the EST connector to set the spark? It sounds like you didn't...

 

Wow that is a lot of info!! Sorry it took a day to respond, I was down with a cold.

I will check into resetting the ECM for 29 injectors. I read all over that people but them in their 86 and 87 vettes and it was amazing. So maybe I do need to adjust for it since I'm getting lean codes.

I will try that with the IAC too. I set the TPS at .54 but still has the problem. I feel like a lot of the problem is the IAC.... I know you guys hate to see me throw parts at it but I put a new pressure regulator in it today (glad I did, the old one was rusted to hell and back) but still having the starting issue and am in the same boat.

Could this be an ECM issue all together? Could the ECM be bad?

The corvette shop said their was some kind of wiring issue in between the IAC and ECM that they couldn't figure out. The FSM led them to a dead end.

How to I reset the ECM for bigger injectors? I checked pressure today and I'm between 30 and 35psi

As far as the RPM, I am just judging from the dash.... When we got timing where it should be the car would die. So am having to run it high (according to the dash) just to keep it running.

 

No!! I didn't know you had to and obviously the mechanic didn't either. Damn these cars... I feel like every repair has some secret code that only the Corvette cult know, haha!!

 

A little beyond what I can do but I'll be happy to charge you money to "cure it" for you?

That is weird. You put bigger injectors and you are getting a lean code? You should be getting a rich code. Besides, you don't reset the ECM. You reprogram it or in my case, you get someone else to reprogram it.

IIRC, your car needs the IAC to be at 0.54V. My car is Speed Density so I have no MAF but I have a air temp and a Manifold Absolute Pressure sensor to gauge air volume. I would set your IAC first then set the TPS. All assuming your timing is right which it doesn't sound like it was or is.

I don't know but it is beyond your capabilities to test the ECM. The rebuilders can do it but I doubt you can without the testing equipment.

They can't figure out. Either the ECM is bad or the wiring is bad or the IAC is bad if we go from one end to the other. Sounds like this shop is bad.

Take out the eprom, UV light it, reprogram it. Pretty simple if you know what the program is doing and if you have the tools. Most people don't except those who delve into that sort of thing As such, it is a job you either need to learn or farm it out. I suggest the latter.

EXACTLY how did you check it? With the engine running? Was the hose to the manifold off?

First off, I don't know if your tach is right. Second, how did you set it? Did you take the wire off and use a timing light? Based on your previous reply, you didn't. As such, your timing could be anything and everything

 

Please don't insult mechanics. If he didn't know how to, he is not only NOT a mechanic, he is an illiterate moron. It is in the FSM and pretty much ALL, not most, ALL L98 engines I have seen. Without disconnecting the wire, the ECM will advance the timing to what it wants and you will never be able to set it right. You need to stop the computer advance so you can set it to 6 degrees. After which, you will get a MIL (Malfunction Indicator Light or Mother In Law) code which you will reset with your scanner

Nope. No secret code. But if you feel that way, I'll be glad to sell you my secret code book for the low, low price of $99.99. And if you buy today, I will take care of shipping and throw in a set of Ginsu knives. Please act fast because you know we can't do this all day long. I take cash only. No exchanges or refunds.

 

I think you meant TPS instead of IAC. You don't "set" the IAC -- that is done automatically by the ECM every time the engine is shut off or started. You should set the TPS as part of a minimum idle adjustment:

https://www.corvetteforum.com/forums...post1570563689

I suggest that you NOT do this. The original EPROM is gold and you should never mess with it. New EPROM chips are a dime a dozen, so the way to go is to program a new one. The tuners have plenty of them.

The ECM sets the idle timing to 20° BTDC, which is roughly 12:00 on the harmonic balancer (usually the groove is blocked by various accessories and you can't see it). To set the timing, disconnect the EST connector, which is a single pin connector between the windshield wiper motor and the brake booster. It has a tan wire with a black stripe. It's probably buried in the wiring somewhere in that general area. This is what you're looking for:



After setting the timing the ECM will hold an error code 42. You can erase the error code by disconnecting the ECM reset connector for a second or so:

 

Haha, you might as well take my money, everyone else has

The shop both times when they did the timing just had the timing light and turned the distributor until it seemed right. I am guessing that is wrong?

I will need someone else to do the reprogram for sure, that is way beyond me!!

I did the screwdriver injector test to hear if they are working and all of them seem to be firing good.

I really think it might be an ECM or wiring issue. At this point I have pretty much rebuilt the damn car, hahaha!

I will pull the ECM and have it tested and then if it's good have it reprogrammed for the larger injectors to see what happens. When I pulled the codes yesterday it gave me 12 different trouble codes. If that was true the damn thing wouldn't be running and driving

I will keep you posted! Thanks for the help and let's see what happens.

 

Thank you for showing me this, I didn't even know this thing existed. Like I said I am so new to this and can't thank you all enough for guiding me through this stuff.

I didn't ever know what an EPROM is, haha!! I will look into that also. How do you program them? I am guessing I should find a "real mechanic" to do this?

The TPS I have adjusted a million times and seems to not affect anything for some reason.... I have even messed with it with the car running and didn't do anything. Is that normal?

Thanks!!

 

My bad. TPS is 0.54V. I don't like the procedure you mentioned because you had to be sure that the command idle is stock. Setting by IAC counts does not.

Whoops. Mine has been erased quite a few times. Not that it does me any good as long as the tuner is competent. I lost the backup too. Actually, I don't know if tuners have that many since our cars are scarce. Harder to find people who have the desire to tune the old stuff so if you are sure, I might have to get a blank chip or two as a spare