Hello, I am stationed overseas in the US Military, recently purchased a 1989 IROC, 350 TPI and 64k miles. This car has sat for a long period of time. Car starts up and runs great for about 3 minutes. As soon as the engine comes off of high idle and starts to warm up, the RPM's start jumping around from 1000-500 RPM and the engine starts to miss. Eventually the engine does shut off, but can then be started right back up again without issue. I have replaced the coil, distributor cap, rotor and pulled #1 plug. The plug looked good with no carbon build up. Also have replaced the fuel filter and plug wires. Any ideas would be greatly appreciated on what to check next? TPS, MAF, injectors?

 

IT seems to run fine in open loop, but then falter in closed loop operation if I am reading right? First things to check would be the MAF and ECM. Also, do the RPMS do a constant cycle up and down between 1000-500? That sounds like a vacuum leak.

 

Yes, the engine constantly is jumping around between 1000-500 RPM until it cuts off. I do have a gasket set for the intake assembly and may try to change the gaskets this weekend. Also will check all the vacuum lines and verify that there isn't anything split or dry rotted. Will post results, thanks for the input Gunner.

 

If it's running well in open loop but stumbles in closed loop, I'd change the O2 sensor. My GTA has 35,000 miles on it. But when I changed the O2 sensor last year (the original factory one) it was pretty much burnt out upon looking at it.

 

Thanks Reid, I have a three wire heated O2 sensor and harness that I plan on installing this weekend. I just happened to have it sitting around from my TPI install in my 55 Chevy. Thanks again for the recommendation.

 

Just a note of interest... today while running the car, I noticed it's running really rich. Any ideas? Ordered new MAF, IAC and injectors today. Getting tired of messing with this car. I have only owned it for three weeks and it's wearing on my last nerve.

 

well my only thoughts on this is timing chain and your tpc, timing could be all ****ed up and once the high idle comes down the off timing could be much more eveident to where it is unable to run. or the tpc but i doubt it. oh wait i had a similar problem, the sensor underneath that has the big plug, i thinkn the map senor, mine was all kinds of black, i took some carb cleaner to it cause i didn't have the money to get a new one at the time and it made a big difference!!

 

if his timing was f'ed up the car would ALWAYS run terribly....... its either the MAF sensor, or the o2 sensor...... its going to be something that the car ONLY uses in CLOSED LOOP (when the car is warm) to check if the car is in closed or open loop, you can connect the A and B terminals (i believe, don't call me on this) on the ALDL port (OBD-1) under your steering wheel with a paper clip. if the light blinks fast, the car is in open loop, if the light blinks slow, it's in closed loop....... hope this helped

 

Thanks for all the inputs, new O2 sensor going in today. I am swapping over to a three wire heated O2 sensor as I have heard it's a good mod to invest in? New Granatelli MAF on order and injectors. Pretty much going to disassemble the entire TPI plenum and rebuild it from the intake manifold up including new ACCEL injectors. Thanks bigchief with the quick diagnostic service check procedures.

 

hey no problem man...... i've had my 89 bird for ever, and i've diagnosed i think every problem possible haha....... i had that exact problem for a while...... i've pretty sure it ended up being the MAF sensor, those things don't come cheap, but they are definitely a necessity..... as that other guy said, check your vaccum everywhere near the back of the plenum on the passenger side, also theres that vaccum line under the throttle body, check that too. you could even use carb cleaner in the MAF sensor you have, just spray that thing good, let it dry, and smack it back in. thats made a big difference for me in the past wehre mines gotten dirty

btw, my bird has about 250,000 miles......... these things run for ever, you just need a little patients. also with my experience, changing the computer has fixed problems for me in the past, i've had codes pop up, and would NOT go away, and once i changed the computer, the codes went away.

 

Well... it's not the O2 sensor or the TPS. Replaced both and still the same problems. When I first got the car (3 weeks ago) I removed the MAF and sprayed some carb/choke cleaner inside. Lots of brown dirt came flowing out. This car has sat for a long time. Hopefully when the new MAF and injectors get here that will fix the problem. Want to get the car running well and start driving it now that the weather is nice. Will be sure to chime in whenever I get the problem fixed.

That's pretty impressive that you have 250,000 miles on your Firebird.

 

haha yeah, its getting painted, should have it back soon....... i've been without it for too long, i'll post some pix of it if you want

but yeah, the idle problem drove me crazy with that car........ as i said, it was either the maf or the ecm...... everything else on the car is ok, but i remember litterally pulling my hair out b/c the thing would NOT idle smooth..... but once i fixed that problem, its been running like a champ. i did rebuild the motor and tranny though, among other things.........

 

Please post pics after you get it back from paint. Always interested in what other people are doing with their rides.

I guess I can't complain too much... after all I only paid $1600 for the car, has 64k miles, new paint and is in pretty good condition overall. If I can only get the T-top leaks fixed and get the engine running smooth... I'll be ready to cruise the Japanese beaches. I guess I'm so frustrated because I just finished installing a TPI system in my 55 Chevy and it runs SOOOOOOOOOO smooth. Now I bought a car that originally had this fuel injection setup and it runs terrible. Hopefully will have the new MAF this weekend. Where did you get your replacement MAF?

 

Unplug the maf sensor and start the car and see if the problem goes away, if it does, it probably means the maf sensor relays are bad (the 2 oval relays on the firewall near the brake booster) I'd change those first before swapping a new maf sensor.
also check for vac leaks.

 

I'll give that a try today. Thanks for input.

 

Well here's my update on my troubleshooting progress. I finally was able to get ahold of a Chilton's manual and conduct the Diagnostic check by jumpering pins A and B on the diagnostic connector. Unfortunately, no trouble codes popped up. What does this mean? Are all my sensors and good and I should then assume that my ECU is faulty? Could my distributor module be faulty? Any ideas of what to look for next? I did unplug the MAF with the engine running and with no change. The idle was still rough and the RPM's still jumped between 1000-500 before eventually cutting off.

 

If you can get your hands on an ALDL cable and a laptop or a scanner, then a short datalog would probably indicate where the problem area is. With no codes, it is time for more methodical diagnostics.

In the spirit of throwing parts at a problem, I know that a faulty coolant temperature sensor can cause the engine to run rich and cut off once it gets warm; however, when it went bad on my car it threw an error code. The sensors are cheap (less than $15).

 

had same problem w/ my 87. changed MAF and reset TPS to correct voltage and problem fixed. also may be a good idea to clean and reset your IAC. know what the problem is b4 you go and replace parts. would also check for vacuum leaks especially around your EGR.

 

Thanks for the assistance, so far... here is what I have on order (hopefully will arrive this next week): new ACCEL 24lb injectors, New IAC, New Granatelli MAF, New ECU w/memcal, New coolant sensor. I really don't have much choice in throwing multiple parts at the problem considering I am living in Japan where TPI parts are not plentiful. I simply cannot run down to NAPA, Autozone or Kragen to get my parts, I have to order and wait. formula_pilot... the coolant sensor is also going to get changed out. Cooling fans run continuously from the time you start the car. navyCM, what's your story? You a fellow shipmate?

 

yea im a seabee, a CM1. i would not recommend the granatelli MAF. i have not used it but was going to get one when i replaced mine an saw alot of bad reviews on it on here. you dont need to throw a ton of parts at it to fix it. this site as tons of good info on how to troubleshoot issues. do a search b4 you spend $$$. your ECM is probably fine they just dont go bad. if you jump your ALDL w/ a paper clip the first code you see should be a 13. your SES light will flash once for 1 break then flash three times for 3. this will tell you your ECM is working fine.

any other codes in there will flash the same way after the 13 flashes 3 times in a row.

 

Something else not mentioned is the Sensor in the distributor, having brain fart on the name. Also the pickup coil in the distributor. If its sat for a while, that pickup coil could be rusted, along with the tabs it reads.

You can test the pickup coil with a volt meter.
the sensor can be tested if you were in the US. Doubt they have the test tools on that overseas. If you go to replace this sensor, a performance one is not needed, just get a delco replacement.

 

Thanks for your assistance CM1, unfortunately the Granatelli MAF is enroute and will probably be here on Tuesday. I did the ALDL jumper yesterday and didn't receive any fault codes. Code 12 flashes 3 times but nothing follows. Car did sit for a while so I will check for rust or corrosion inside the distributor. I did replace the cap and rotor already but didn't pay any attention to the other components inside. Thanks again.... STGC
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I will take a look at that component for corrosion. Yes, the car has sat for a very long time. Probably wasn't driven for the past 2 years or so.

 

Did you do a fuel pressure check? I don't think your problem is in the sensor or computer system. It sounds mechanial. Do this before you change all of those parts!!! Get a fuel pressure guage and screw it into the test port on the rail you should have at least 36 psi at idle and watch what happens on the guage when it starts running poorly. You could have a weak fuel pump..

DO IT BEFORE YOU CHANGE ALL OF THOSE PARTS!!!!

Also did you put a timing light on the spark plug wires and watch the pulse when it starts running poorly. The pulse should be nice and smooth on each one of the wires. If the pulse becomes erratic the problem it in the ignition system. Start buying test equipment before the parts.

Also, I had the Granatelli MAF and it was a piece of junk. Caused alot of problems. I returned it.

 

exactly, well put burnout88. buying tools and test equipment is NEVER a waste of money. buying parts you dont need is. find your problem b4 you throw parts at it. youll spend more money doing this than finding the problem and fixing it w/ the right part(s). plus you will learn something.

 

I would find it hard to believe that my fuel pump is weak. After all, it runs so rich now that it burns your eyes to stand near the car due to the fumes. Not going to spend a crazy amount of money on test equipment for a car that is going to get sold in two years after I have had my fun with it. Parts are ordered and at the post office. Replacement of parts on an old car that has been abused and then parked for an extended period of time is always a good idea in my past experiences. This is going to be my one and only authorized car for daily driving due to base policy, so it has to be as reliable as possible. Will post results AFTER I swap all the parts. If it doesn't fix the problem... then the car is being sold for a blower project and the TPI system is being swapped into a 62 Impala with a MAP conversion and new wiring.

 

i dont mean to be rude or disrepectful, but if that is your intention for the car ill buy it and ship it back here to a loving owner. you have no idea what it is you have on your hands. just b/c it runs rich and burns your eyes has nothing to do w/ the fuel pump. if you fix that car properly you will have no regrets. we are trying to help you spend the least amount of money possible. if you want to buy tons of parts to throw at it that is up to you, but you are wrong. how can you go wrong w/ test equipment? itll work for whatever ride you have.

ive been a mechanic for a long time. changing parts is not the answer. troublshooting is. even if you have no intention of keeping the car why not learn something while ur at it. in all honesty if you dont want to fix the car properly sell it to someone who loves these cars b/c yuou obvisously have no idea what you have.

again im not trying to be rude or **** you off its just the truth. so dont have any hard feelings...

 

Trust me.. I'm not pissed. I have received many valued and appreciated inputs into the possible repair of this car (MAF, ECU, fuel pump, etc). I know what I have in this car and have no regrets in the purchase. In two years when I retire and sell this car, prior to my relocation back to the US, I'll have no regrets then either. Just so you know, I'm not new to auto mechanics. My list of built/restored cars includes: 67 Firebird conv., 68 Firebird, 69 Camaro SS, 69 GTO, 66 Lemans, 73 Corvette Stingray 454, 93 Camaro Z28, 2 x 91 Camaro RS, 04 Dodge Ram SRT-10, 55 Chevy 210 w/TPI conversion. Again, I'm no novice and not new to building cars. When all the parts have arrived, I have every intention of installing them... except for the Granatelli MAF until I get more feedback as to what problems people have experienced.

 

I just got done installing an 88 TPI setup from an Iroc on my original L69 in my 87 Monte SS and I LOVE the TPI. I haven't had a chance to mess with it or drive it very much since the swap which I completed about a week ago, but there was one time that I noticed my car did the same exact thing you described with the up/down idle (it reminded me as if it had a REALLY-REALLY big cam) but when I turned it off and started it right back up it never happened again, and still hasn't happened since that one time.
I know there are a few adjustments one should make after a swap such as this, but I have yet to even do these thing. I'm not driving it yet since I am unable to find the time to do everything correctly as far as the TPS adjustment, minimum idle adjustment, etc, etc.
I've seen a couple people mention the TPS and I'm just wondering if that is something that could have caused my incident? My MAF is pratically new. My O2 is brand new(factory 1 wire replacement).

 

Thanks for your input. I recently installed a TPI stand-alone system on my 1955 Chevy (pic attached) and I agree that the TPI system is awesome. Throttle response is great and it's easy to install on something that never came with the system. I have replaced my TPS and O2 sensor, but still have the same issue. I have disconnected the battery numerous times for an extended period of time and still the same problem. Thanks again for your input.

 

very nice job. looks super clean.

 

Here's mine if I can figure out how to post it.......

 

Looks like a perfect fit, just like it was made to be there from the factory. Wish that GM would have installed the TPI system in more than just the F-body and Vette. Would have been a great addition to the Monte SS. Here is a pic of my completed car. Features a C-4 Corvette suspension front and rear, MAP system TPI conversion and a TH-350 w/shift kit. Interior is tricked out with a Dakota digital gauge cluster, Polished Flaming River steering column. Car was restored in Yokosuka Japan from March 07-February 08. After driving the car, my friend has now decided to convert his 62 Impala to TPI.

 

WOW!!!
That is a beautiful car!
I'm just an average back yard mechanic, obviously you have extensive automobile talent.
I did my swap in less than a month working limited time on it, but I can't believe how quick the car above was done.
AWESOME car!

 

very very nice!

 

Thanks for the complements. I can do just about everything except bodywork. That is one talent that I just don't have the patience for. My Japanese bodyman didn't sleep or take any days off while he restored my 55. After completion it was featured in a Japanese car magazine and kind of put him on the map. Now if I can just get my 89 IROC to perform and run as well.....

 

you should repost this over in the tech/general section, you will probably get more help there. From what you are discribing it sounds as if the car is running just fine until it hits closed loop. That would almost defently mean its a sensor related problem since the ecu ignores them until it reaches closed loop. Maf is really easy to rule out simply unplug it and start the car, if the problem is no longer present you have a bad MAF sensor or relays.

 

If you are positive you installed the TPS properly I'd start looking at the egr valve as the symptoms you are discribing could defently be an egr issue. Do you know how to test it? As far as the new pcm, chip, injectors, MAF sensor and such you should really just diagnose and fix the problem instead of wasting money on unnessicary parts. FWIW I've heard nothing but bad things about accel injectors, doesnt sound like anything is wrong with the injectors you already have so I'd stick with them for now.

 

Thanks for the input. The EGR looks new and is not all rusted up like others that I have seen. However, I do have a spare sitting around that I will install with the rest of the parts. I have had great luck with the ACCEL injectors on my 55 Chevy and have known others in my area that also have had good luck with them. Will be swapped out this weekend. No, I do not know how to test the EGR valve. Please relay the test information if you have any.

 

Aaron

love the '55 chevy setup... maybe you could help me?? I'm installing an '89 TPI into a '54 Chevy. It's physically in and I have a new loom for it but am very confused over the vacuum line setup. (Power brake/ pedal etc.)

can you give me any advice please?

Alan (England, UK)

 

I had very similar symptoms with my son's '89 GTA. Checked the ohms on the injectors and 3 were bad. They should show approx. 16 ohms. Bad injectors will not throw any codes. Since you are replacing them anyway, I guess you can skip checking them. We bought the new Accel (silver top not yellow) and have had no problems whatsoever.

 

probably be better off sellin car maybe get somethin a little easier to work on , not that a tpi stock engine is hard to diagnose with a few simple tools but because an egr valve is not all rusted up doesnt mean its bad if u cant figure out out how to test one ,goin out an buyin a new oneis not the answer,maybe a repair manual like haynes or chilton will help you get the basics of efi an they show you how to use testing an diagnosing equip.

 

I remember a guy telling me about a problem he had similar to this also and he spent a ton of $$$ trying to diagnose/swap out parts including a few different TPS, etc, etc.
He finally for whatever reason swapped out the TPS plug-in connector and it fixed it. I know they are voltage sensitive, so you have to solder the the connections and shrinktube it to do it right.
I have been part of this conversation for a few replys, but can't believe I never thought of mentioning that. Of course I can't guarantee that is the problem, just thought it was worth mentioning. Something else to add to the list

 

Nope.. not selling. Thanks anyway.

 

madmonk... sent you a PM with the vacuum line routing that was used on my 55.

 

then i would take it to a auto shop if you cant test tps voltage or fuel pressures or the 5 other simple things these guys have tried to tell . doesnt sound like you can do everything on cars except for bodywork to me. and i dont think accell 24lb injectors r gonna help u ,their to big. let us know how the maf sensor worked for ya

 

Ha ha... you're funny. You must be a comedian in your spare time. Funny how 24lb injectors have worked for me in the past on other TPI engines. Glad to know that you don't have any idea what you're talking about. Thanks again, happy motoring.

 

the code is 12 not 13...

 

Thanks donaldw, unfortunately no codes are being displayed after the 12. Fuel pressure is always 43 psi, new IAC valve installed, new temp sensor installed, new ECU w/new stock GM chip installed, new Granatelli MAF installed, New MSD coil installed, new distributor cap and rotor, new plugs, new wires, new vacuum lines, new fuel filter, new TPS (voltage set to recommended specs).... and still the same problems. Runs great when you first start it in cold start... then after it warms up, engine starts missing and idle is from 1000 to 500 until it dies after 15 minutes of run time. Getting ready to start going wire to wire and take resistance readings.
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haven't swapped the injectors yet... rainy season here. Rains everyday. Resistance readings are 15.9-16.1 ohms on each injector.

 

Ok so it appears the throwing parts at it isn't working, ready to start trouble shooting? Just for the heck of it when it's stumbling pull the vac source to the egr valve and see if that helps at all and let us know what you find.

 

What about the parts I mentioned above?


ICM is the one I was having a brain fart about.

Pickup coil can be checked with an ohm meter.