BrettWithVette

hey i got an 85 corvette with a 357 in it and for the past week every so often every time i push in the clutch the rpms drop and the car dies its really strange it gives me a check engine light and it will keep doing it for a little bit then it seems like it will fix itself it will drive really poor to very sluggish and jumpy and no power it smells like its burning really rich. i took it to the shop and they told me they think its a mass air flow sensor ANY SUGUSTIONS?? what do u think would a mass air flow sensor do that. its not really a part i can just buy and test out its about a 250 doller part!! please help :sad:

85blkZ51

Do you have any check engine codes?

85blkZ51

If you havent pulled the codes try this,.... With the engine warmed up and idling, gently tap on the MAF. If the engine RPMs drop noticeably or if the engine dies, replace the MAF. I got this info from a book by Ben Watson."How to Tune & Modify Chevrolet Fuel Injection" It is a very good book and worth the money.($16 to $18) You can probably get it at any book store, the ISBN code is 0-7603-0422-x. Hope this helps.

rsafier

Sounds like a likely suspect. You can try that tapping deal, but since you do have codes just jumper A & B on your diag. connector and get the codes. Will tell you immediately what your issue is.

ZylaRace

Another way to test the MAF:
Disconnect the MAF. Start it up, and take it for a drive.
Does the problem go away? Yes = replace the MAF.


(Basically what the Helm's manual say's.)

BrettWithVette

Yea there is codes but i havent pulled them yet but, i did put a brand new maf sensor on today just to test to see if that was the problem i cranked it and it died again every time the clutch is in and the check engine light is still on and its still giving me the same problems its weird i dont know how to explane it i give it gas and it basacally nosedives and surges and chugs and doesnt have any power its really anoying espasally cause i know its hurting my new engine that i put in i dont want to flush the new rings my dad told me that he wants to pull the hypertech performance chip that we put in and see if it will run any better any ideas or comments i could really use them

SBNova

STOP where you are. If you have codes/ check engine light,- READ THEM. It takes two minutes and no special tools to pinpoint your problem. Stop chasing your tail and look at what the computer is telling you.

Get a paper clip, and look up the code number, or just post it and someone can tell you the problem.

84whitevette

I agree with the above post... read the codes, it may be something simple. You'll be replacing all sorts of things that may not need to be replaced.

Pete

BrettWithVette

Wellll good news i bought it home and it didnt run very well so i hooked it up to the machine and got 2 codes an egr fail and a map fail code so i reset the ecu by undoing the battery and now i have no codes any more and the car seems to run ok i thnk those were all codes that were in the ecu memory i hope ill drive it to work and ill see if this mess is finnally over thanks for all the susgestions.
brett :) :party:

jackdaroofer

:cheers: I had intermittent MAF problems, did the tap thing, etc

Turned out the power relay, not the burn off relay was in the process of failing, replaced both relays, cheap, works great
:seeya
:steering:

BrettWithVette

well it started acting up this morning so im glad the map sensor isnt the problem what sensors did u replace we were going to try to replace the stock chip back in and see if the hypertech chip is messing up then we got another idea saying that the plug in to the map sensor may be bad any ideas?

JADVette94

I'm not much of a mechanic, but I had a similar problem on a camaro I used to have. It turned out my fuel pump was dying. I replaced the pump and the filter and the problem went away. Of course, if that is the problem, your computer might give a code for it, I'm not sure.

Bluevette85

85's don't have MAP sensors. What is the exact code you are getting? I can scan the shop manual and send you the diagnostic procedure for the code.

Could you have a leaking egr?

BrettWithVette

typo MAF not MAP

jackdaroofer

:cheers: I was fortunate enough to get an EZ link scanner from another Forum Member and what I found before I got any hard or soft codes was that the MAF was pushing the outer limits and from time to time exceeded those limits.

That was my first clue there was a voltage problem and i ignored it until the relay definitely went south.

I think, and this IMHO, that some conditions have to be beyond the envelope before you get a code

If you have access to a scan tool, you can get readings under different conditions and compare them to the stated values in the manual

:seeya

:steering:

BrettWithVette

ok guys well this is test like 5 or 6 but i changed the plug in that goes into the maf sensor and allas still no difference..so after lot of swearing i dicided to pull my hypertech performance chip :cry altho it was hard to say good bye to it i think this might have done the job i ran it for about 30 min killing and restarting it and it seems to run fine but who knows what the morning will bring. im not really sure that i have even lost a lot from the chip i have heard from other corvette guys at work that hypertech chips are not the way to go and they are really bad espacally in corvettes but i do not know about all of that i will be a strong beleaver if this works though and the hypertech company will be hearing from me :mad but well see if u guys have had any experenced with hypertech let me know

CentralCoaster

Sounds like it won't idle. Have you verfied the setup of the TPS and IAC? If the intake doesn't see a vacuum leak at idle (or clutch in, no gas) it'll run like crap.

Sounds like you might just be down a cylinder. I was driving my vette yesterday on 6 cylinders, so I know what it feels like! :eek:


[Modified by CentralCoaster, 3:34 AM 3/25/2004]

alfonso gomez

I also have a Hypertech Thermomaster chip on my basically stock L98 1987 Coupe. I have no problems with it. IMHO, it should work fine in a stock engine, it does in mine. Of course, if you change the cam, have ported heads, headers and improved induction, the way to go would be a custom-burned chip designed for your specific engine. I noticed an improvement in the seat-of-the-pants dyno, specially at WOT.
As for your troubles, it is easy to pull the codes. Jump terminals A & B in the ALDL (top row, the first & second terminals from your right) using a bent paper clip with the ignition in the OFF position. Then switch it to the ON position without starting the engine or you can fry your ECM. Watch closely the SES light. It wil give you a code 12 (1 flash, 2 flashes) three times. That indicates the ECM is in diagnostic mode. Then it will flash a code 33 (3 flashes, 3 flashes) three times. This indicates a problem with the MAF sensor. If it gives you a code 36 (3 flashes, 6 flashes) the problem is the burn-off relay circuit. To troubleshoot code 36 it is better to have a GM shop manual and follow the directions there. All codes stored in the ECM will flash 3 times. After the last code is displayed, it will show code 12 three times to let you know that the diagnostic mode has ended. Then, switch the ignition to the OFF position and remove your paper clip from the ALDL before attempting to start the engine. Hope this helps. Let us know the outcome.


[Modified by alfonso gomez, 8:39 PM 3/25/2004]