Hello there,

I have a 1988 Iroc-Z TPI with a 700R4.When I start the car hot or cold the car will idle at roughly 1500rpm. When I put it in Drive it will idle down around 700 which is where it is supposed to be around. I cleaned out the throttle body and IAC. When I started the car it idled at 500rpm then after running for a minute it would stall out. I then set the TPS 0.54volts and 4.0 volts at WOT, went through the whole procedure and bench tested it and tested the wiring harness I know the TPS works and gradually increases voltage as intended. Then the car idled perfect, purred like a kitten as if it was brand new and drove perfect. Parked it and started it up again and all the problems I had before have returned:

High idle 1500rpm in park (normal in drive)
Wants to take off when i put it into gear, I have to ride the brakes while in town
Occasional jerking while decelerating or slowing down

I have also checked vacuum lines they are all fine, as well as went around the intake manifold and runners with an un-ignited propane torch slowly, and i have tried giving the ECM a few taps as some folks have said that was the issue, but nothing changed.

Please somebody give me some ideas I have no idea what else to try here. I am stumped, and confused as to why it ran perfect after the adjustments and then they started back up an hour later when i started the car again and will not go away. I have went through many threads and have no idea what else to try here except throw parts at it.

There are no engine lights on. It will do this on every start up and every time it is put in park.

Thank you all

 

Make sure the throttle blade isn't sticking to the bore.

 

throttle plate is not sticking for sure it is smooth and opens up and closes completely

 

I had the same issue and tried new computer, sensors, vac lines etc. Ended up being the coolant temp sensor connector was bad and wasn't making connection with the coolant temp sensor

 

I will take a look and see JP Camaro thanks for replies I can use any help here, I will keep updates until it is fixed.

 

I have tried everything under the sun, I have no other way except to conclude it is the ecm, anybody know how to go about doing this? I can find a remanufactured ecm (1227165) but no prom? Can anybody give me some detailed guidance on what to do here? If i am to get a new ECm and transfer the prom do i still need to "tune",?

 

If your running a all stock engine. You just need a ecm and you can transfer your memcal over.

 

Thank you, I have a new ECM on order, can you briefly explain the process of switching the memcal over? My understanding is the Memcal contains the PROM and the Cal-pak. Is it just a plug and play? or do I have to desolder it out of my current ECM and solder into the new one?

 

The chip swap on the 1227165 is as simple as removing the access plate (two screws) and pushing the button like it says.

 

Much Much appreciated I will keep updates on whether or not this fixes the issue thank you all for any and all help!!

 

Also try checking the throttle shaft to see if it's losel and has a vacuum leak. Do you have a cable to connect to a laptop to run a data log?

 

I dont have a a cable but I do have a laptop and Tuner ProRT , only thing is I would not know how to read the data, how do you know what is up and what is out of place when reading the data? I wish I knew but do not know where to start. I have the ECM out now, and notice it has an "ADS Superchip 1987Tm" must have been put in 20 years ago from previous owner, but it always ran good till recent. Not the original PROM I suppose if it has this chip. Also, I cannot find an exact Serv No. to match 1227165, but other ECM's that come up as remanufactured equivalents from part stores. Not sure how to go about it...

 

Now is a good time to PM Tuned Performance, (post #7) He can replace the "Stupidchip" for you. Your ECM may be good.

 

The 165 service number has a few superseded numbers for remanded units.
16198259 ,88999194 and 77-7165 are all the same ecm.

 

I would try a ecm first lol, if the superchip is bad you would get a code 41 or 51. If it has lost data on the prom a bit has flipped you would be running rich and in limp home mode.

 

Good advice.

 

Another test you can do is wrap on the ecm case while the engine is running good. See if it stalls out or runs bad. This flexes the circuit board slightly. The 165 ecm has been known to have solder joints come loose. I think this has been addressed with supersede service numbers.

 

Thank you TunedPerformance and Redrock. I have tried tapping the ECM and dont notice anything. I will try a new ECM and see what happens, its good to know there are other part numbers I will plug it in and see what happens. I have no engine codes so chip is probably fine it has been in there forever and worked alright, you could be right about the solder joints or something may not be right on the outputs. If not I may PM TunedPerformance as Redrock suggested, but I would not like to bother someone until I absolutely have no other choice. I will try the ECM change and keep an update. Again.....I really appreciate everyone's time and help Thank you!!

 

Are you suggesting its possible a bit may have flipped causing a rich condition aka the high idle issue I am experiencing?

 

No I don’t think that’s your issue. If it was you should have a code for the memcal.

 

Update. So i bought a new ECM...car would not start with it even though it looked the exact same and the pins fit (yes the memcal was switched into it and was plugged in the right way). It was a BlueStreak "EM7165S" and it is the only one I could get around here which is suppose to work to replace my 1227165. Anyways put the old ECM in and car had a hard time starting. Everytime I unplug the ECM out and put it back in the car has a hard time starting got to floor the pedal, but once it starts up its fine after that. But would not even try with the new ECM.

When I do unplug the ECM it idles normal until I drive and park it again then the high idle comes back like usual (1250-1500rpm in park hot or cold, 700-750 rpm normal in drive). But at least I know if I unplug the ECM a complete ECM reset happens (if you want to put it that way) and it idles ok momentarily, or at least till it relearns and starts idleing high again.

Any new ideas? Only thing I havent tried really is the EGR because of its location under the plenum, could it be stuck open causing this?? I wonder if the Innova 3140g OBd1/OBD2 scanner would work for OBD1, maybe I can try that to scan and see, Ill call innova to see if it will also scan OBD1 (I know it scans live data OBD 2)

Any more ideas are greatly appreciated.

 

Have you adjusted the IAC (idle air control)? https://www.thirdgen.org/tpimod2/ or maybe it is faulty.

 

Brake booster diaphragm might have a hole in it. It would cause a pretty good vacuum leak. How are the brakes?
Test it with a vacuum pump, or remove and block the line to see if anything changes.

 

Yes IAC has been adjusted and cannot adjust down anymore. And I have also checked the brake booster. Brakes are good.

I notice if I remove the rubber boot in between the MAF and the throttle body it will idle good (leaving the MAf plugged in). No engine codes.

 

All of a sudden getting Code 45 (rich exhaust mixture) at random on and off, Might have to spring for a MAF sensor.

Anybody heard of a MAF sensor causing these issues along with high idle in park/neutral?

Just hard to choe down the cost of a new MAF here they are very pricey.

 

[QUOTE=BlksIrocZ;6232337]All of a sudden getting Code 45 (rich exhaust mixture) at random on and off, Might have to spring for a MAF sensor.

Anybody heard of a MAF sensor causing these issues along with high idle in park/neutral?

Just hard to choe down the cost of a new MAF here they are very pricey. Any recommendations on what MAF to get??

 

You should post a ad in the wanted classifieds. I would go with a used Bosch over a aftermarket maf.

 

Hey TunedPerformance it is EXCEPTIONALLY HARD here in Canada to find parts especially used for TPI thirdgens. Very rare to I even find other TPI owners, every time I think I do they pop the hood and there is a carb. I am very much alone up here. Do these symptoms we discussed on this thread spark anything to you relating to a MAF? Anyone please chime in here:

Symptoms:
High idle
Occasional idle surge(hunting)
slight acceleration on its own from a stop until reaching around 50km/hour
Jerking while decelerating from 100km/hr to around 70km/hr
Sometimes will not start unless holding throttle plates open and throws code 45(rich exhaust)

All of these symptoms are random and no real consistency (except for the high idle which is 90% of the time, very rare will idle normal) they happen on and off at random warm or cold night or day

I am so lost and getting desperate I have had everyone I know come look at this with me now also and everyone scratches their head.....including mechanics however some say maybe the MAF but I can only get a remanufactured one no scrap yard in the country has one used!!!!

Nowhere I look on the threads here (days and days of research) point out these symptoms as a MAF issue, No code 33........

 

Hey TunedPerformance it is EXCEPTIONALLY HARD here in Canada to find parts especially used for TPI thirdgens. Very rare to I even find other TPI owners, every time I think I do they pop the hood and there is a carb. I am very much alone up here. Do these symptoms we discussed on this thread spark anything to you relating to a MAF? Anyone please chime in here:

Symptoms:
High idle
Occasional idle surge(hunting)
slight acceleration on its own from a stop until reaching around 50km/hour
Jerking while decelerating from 100km/hr to around 70km/hr
Sometimes will not start unless holding throttle plates open and throws code 45(rich exhaust)

All of these symptoms are random and no real consistency (except for the high idle which is 90% of the time, very rare will idle normal) they happen completely at random warm or cold night or day

I am so lost and getting desperate I have had everyone I know come look at this with me now also and everyone scratches their head.....including mechanics however some say maybe the MAF but I can only get a remanufactured one no scrap yard in the country has one used!!!!

Nowhere I look on the threads here (days and days of research) point out these symptoms as a MAF issue, No code 33........

 

[QUOTE=BlksIrocZ;6232592]Hey TunedPerformance it is EXCEPTIONALLY HARD here in Canada to find parts especially used for TPI thirdgens. Very rare to I even find other TPI owners, every time I think I do they pop the hood and there is a carb. I am very much alone up here. Do these symptoms we discussed on this thread spark anything to you relating to a MAF? Anyone please chime in here:

Symptoms:
High idle
Occasional idle surge(hunting)
slight acceleration on its own from a stop until reaching around 50km/hour
Jerking while decelerating from 100km/hr to around 70km/hr
Sometimes will not start unless holding throttle plates open and throws code 45(rich exhaust)

All of these symptoms are random and no real consistency (except for the high idle which is 90% of the time, very rare will idle normal) they happen completely at random warm or cold night or day

I am so lost and getting desperate I have had everyone I know come look at this with me now also and everyone scratches their head.....including mechanics however some say maybe the MAF but I can only get a remanufactured one no scrap yard in the country has one used!!!!

Nowhere I look on the threads here (days and days of research) point out these symptoms as a MAF issue, No code 33........

 

The only way I could say condemn the maf. Would be odd grams per second readings while datalogging. You might want to pick Vader’s brain on what maf to get and if he thinks it could be a maf. Without reading back through your thread I forget does it run any better with the maf unplugged ?

 

It runs VERY rough without Maf (typical MAF failure sound) which I used to get when I had a failed burnoff relay, which I kept getting for years until I found one that worked. And will idle around 500rpm almost stall but will run

 

You could always ways ask someone to ship to Canada . It’s a reman but it’s a Bosch
https://m.ebay.com/itm/1988-89-Fireb...9a34%7Ciid%3A1
It states 88-89 but will work with 86-89 tpi maf

 

I will choke down the cost of the MAF (and will try and get a datalogger for the future whether or not it fixes the problem or not to prevent diagnostic issues like this).

Ill keep a report if it fixes, or whatever fixes it...I will not give up. Also anyone in the future can read this thread and hopefully it helps them. It is definitely a unique/unusual issue I am having.

Thanks again

 

Have you checked the throttle position sensor and made sure that it is reading correctly? And, carbon build up behind the throttle plates will cause it not to close completely and idle high. I know you said that the plates open and close smoothly, but do they close completely? And does the throttle position sensor know that they're fully closed??

 

Yes TPS voltage is 0.54V closed and roughly 4.0V at WOT. I also bench tested it to ensure it sweeped smoothly checking the resistance. Throttle body is polished clean now no carbon build up left in there including the IAC.

 

Having a spare maf wouldn’t be that bad of a thing to have. I bet the shipping and import tax is the real killer. Looking for a c4 salvage yard might be another option but you never know what your getting .

 

I found a Remanufactured one here from a parts store, it just scares me because I heard a lot of horror stories on other threads about them not being any good and miss calibrated.

 

I think some even get away with the burn off function causing error code 36.
Maybe Vader will chime in he knows the aftermarket maf world pretty well looking at his posts.

 

Looks like his suggestion is Post 14

https://www.thirdgen.org/forums/tpi/...ermittent.html


The one on eBay the link on Post 33 is a cardone or refurbished acdelco 213-3418

I can’t seem to find the airtex/wells on RockAuto.

 

Not sure who vader is but that would be great to hear his input. If the MAF does not work I will buy a datalogger from MOATES looking at the APU1, pricey with shipping and import that's the only thing.....ouch...glad to be in Canada...... Data logging will be new to me, however I am not new to software and computers. If I do go that route I hope you dont abandon me TunedPerformance lol and can give me a shot of advice for what I get for readings.

Thank you all for staying with me here, its highly appreciated. Good to know there are others out there keeping these cars going without the "get with the times and buy a new vehicle" which I keep hearing a lot of lately....

 

I’ll be glad to look at datalogs and hope I could find the gremlin.
Your ecm the 165 can be real picky on datalogging. Sometimes you can’t connect to the ecm or connection consistently drops. Just the bad nature of that ecm. I have no idea if there is a fix for it. When you go to datalog the xtreme aldl has a slide switch with a 10k ohm resistor built in. This needs to be in the 10k mode to start data flow then turned off once data is flowing.

 

Here is a link to the ads data stream file. It needs to be converted to adx in tunerpro rt.
I have had issues with the outcome and update to the 89 $6e mask when I do custom datalog tunes.
http://www.gearhead-efi.com/Fuel-Inj...nformation-32B

 

Ok thank you. Yes the MOATES APU1 datalogger has the 10k resistor switch as well I have done considerable research into. Link provided if it is of any interest.
I will try a MAF first and then see, following that I may order the datalogger, coming from the United States to Canada, may take some time.

http://support.moates.net/autoprom-apu1/

 

The apu1 might be a little overkill unless you plan on tuning live or burning a new prom and it does allow for data logging. You would still need a g1 adapter to install a burned chip to or emulate. This is a cheaper alternative
http://www.moates.net/aldu1-and-cabl1-p-127.html

 

Thanks for the input yes also the HDR1 to download my stock chip which I plan to. Just have to figure out how the G1 adaptor works exactly. I understand I do not have to remove my current chip to use a burned chip which is awesome. Ill keep the thread updated on progress. I thought It may be a good idea so I can emulate in order to play with it and help me learn including working on my high idle (assuming the MAF doesnt fix the issue)

 

Update:

No more running rich after new cap and rotor. When I opened them up it was melted. Put in a new MAF sensor and new coolant temperature sensor also.

I can get it to run right if I turn car off ground the ALDL (let IAC fully extend) then unplug the IAC and unplug the ESt bypass turn car on then plug them both back in (Car will stall down the road with IAC unplugged) I can drive all day with a smooth idle but as soon as I turn the car off it returns again.

This is as close as I have got it to run right in a consistent way without randomness!!

Any Ideas for a next step? Could this be a faulty IAC? Although I have checked it and it moves I know that, and also I checked the resistance of the stepper coils and they are within spec. (Reminder TPS is good)

Still stuck with high idle 1000-1200rpm in park and neutral only.

 

Have you removed and cleaned the IAC? They get gummed up from the EGR. You may also have a cracked vacuum line, or a sloppy throttle body shaft. The hard plastic vacuum lines disintegrate over many heat cycles. You can replace them with rubber vacuum line hose. I know from your first post, you went through all these things, but even a small leak will cause a problem. Also check the throttle body gaskets. Some try and spray carb cleaner on all the runner gaskets and throttle body and see if the idle changes at any given spot. Do this with the engine running. Just be careful of fire. Water spray may be ok also.

 

Thanks Red Rock, but yes I have cleaned it very well and checked the vacuum lines and went with propane thoroughly around the gaskets with no success

 

A possible contributing cause might be a failing or bad catalytic converter. That was one of the reasons my mechanic diagnosed for high idle when repairing my RS. Hope this helps.