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Old 08-02-2010, 11:53 PM   #1
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TPI surging when warm

Hello all. Need some help on my 87 GTA.

The motor is an L98 from an 89 Formula. It is stock with the exception of an aftermarket computer chip. I think it's called a Superchip. Anyway, when I did the swap I put 8 new Bosch III's from FIC, all new plugs, wires, cap, rotor, fuel pump and intake gaskets. The car ran exceptionally well for 6 months. Then the car sat when I went to Korea. My wife would start it every couple of weeks and drive it around the block. There is no check engine light on.

When I came home, I found a bad CTS (SES code). Swapped it with a new one and my CTS problem went away, but the surging problem is still there.

The car starts and runs fine until it gets to operating temp. Then it surges from 400-1200rpms and smells rich.

Please help with any suggestions.
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Old 08-03-2010, 01:19 AM   #2
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Re: TPI surging when warm

sounds like mine, but I swapped new bosch III's and problem went away...how much gas was in the tank while you were gone??? maybe the fuel sock got clogged with all the garbage inside your tank?
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Old 08-03-2010, 12:07 PM   #3
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Re: TPI surging when warm

well the pump and sock are new. there shouldn't be any trash in the tank. i left august 09 and came home on mid tour to the problem in march 10. now, i'm home for good and the problem persists. i don't think it's old gas either because i've already burned through the old tank and filled up.

what about the o2 sensor?
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Old 08-03-2010, 01:43 PM   #4
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Re: TPI surging when warm

have you checked your codes? you know how to do it with a paper clip? you bend it into a U shape and put it in the two holes in the upper right of your diagnostic port, turn the key to ON but dont start, then just watch the flashes. should be one flash, pause, two flashes (that should happen 3 times) thats code 12 (normal op code) trouble codes will flash same way. one set of flashes-pause-then another set. each code will flash 3 times so you catch it. Always starts and ends with a code 12. Sorry if you already know how to do this...only thing I can think of
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Old 08-09-2010, 08:19 PM   #5
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Re: TPI surging when warm

Sorry it took so long to reply. I haven't messed with the car for a few days.

Today I started the car and drove it to pick up my son from school. The SES came on after a short time. Code 33 MAF, and code 44 is what I have. The car is running very rich as well but it has great power and seems to run very well when cruising or under acceleration.

I have swapped the MAF relays around, and still have a code 33/44. I am thinking that the O2 sensor is fine, since it is reading the condition of the exhaust and reporting it to the ECU. I assume that the MAF is faulty, and the ECU is running the fuel mixture from the memory. Is there a way to test the MAF, or to prove that the MAF is bad? I suppose I can get a new one, but I don't want to spend the money if it's not the problem. Any other suggestions?
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Old 08-11-2010, 09:30 AM   #6
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Re: TPI surging when warm

The more I research, the more I suspect a bad MAF sensor. Is there a way to test the MAF?
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Old 08-12-2010, 06:00 PM   #7
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Re: TPI surging when warm

Quote:
Originally Posted by stealth908 View Post
The more I research, the more I suspect a bad MAF sensor. Is there a way to test the MAF?
Aside from swapping in a new one, yes. Unplug the MAF and see what the car does. That will force it to run from the default tables in the PROM.
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Old 08-14-2010, 04:37 AM   #8
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Re: TPI surging when warm

You've probably already checked this, but it could be the TPS(throttle position sensor) I had a similar problem, changed everything from the ESC to the MAF, turned out to be the TPS, not very expensive from what I remember.
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Old 08-14-2010, 06:38 AM   #9
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Re: TPI surging when warm

Check for vacuum leaks, you would be amazed at how a little leak can affect your idle. Then check your TPS calibration and replace if needed. Vader did a very useful "how to" on that subject. Don't assume parts are bad, they just might need a little adjusting or cleaning to be efficient.
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Old 08-14-2010, 04:26 PM   #10
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Re: TPI surging when warm

Thanks for the replies guys. I replaced the TPS when this problem first started. I have adjusted it up and down in accordance with the write-up. I am going to do it again though. I know that the IAC is woring as well.

As for the MAF... I started the car and let it warm up. Then I disconnected the MAF while it when the car was running, and the engine shut off abruptly. I am thinking the MAF is good. I think I will try starting the car with the MAF disco'd and see what happens.

As for vacuum leaks... I bought a can of starter fluid and I will check EVERYWHERE I can for leaks.

By the way, I noticed that the car idles just fine in gear, and doesn't smell as rich. As soon as I put it in Neutral, the surging starts, and there is black smoke puffing from the exhaust.

Thanks so much for the help on this.
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Old 08-14-2010, 10:53 PM   #11
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Re: TPI surging when warm

BTW, I thought I should mention that the car takes an incredibly long time to start when the engine is cold. Actually, it doesn't do any good to sit and crank for extended periods. The only way to get it to start is to do short cranks over and over again. After doing that 10-15 times, it'll finally start. I am going to check the base timing too.
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Old 08-15-2010, 02:32 PM   #12
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Re: TPI surging when warm

When one thing goes wrong you gotta check 10 other parts, gotta love it!! Take a look at the 02 sensor and inspect the wire for any open spots, it's routine maintenance to replace it every so many miles, that could be why your getting code 44, lean exhaust. Unplug the MAF then start the engine, see how it runs and plug it back in while its still runnig, you should notice a difference in the way it runs when you plug it in. I'm not trying to steal 87WS6's advice, I think you might have went about it the wrong way. Check the timing, TPS and MAF then mess with the 02 sensor. Vacuum seems less likely to cause a problem this big.
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Old 08-16-2010, 03:03 PM   #13
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Re: TPI surging when warm

Ok, this is what I did.

I first sprayed the TB with starter fluid. I noticed the engine stumbled and almost died when I sprayed it near the throttle blade shaft on the drivers side. This happened 3-4 times. Then for some reason it wouldn't do it anymore.

My next step was to remove the TB and check for play in the shaft, look for bad gaskets, and clean it if need be. The shaft has noticeable play in it on the drivers side. I don't know exactly how much will cause a leak, but it's noticeable. You can see the blades move fore and aft. I didn't see any bad gaskets, or other problems.

Then I replaced the IAC. I had an extra, so I figured I'd try it. I bolted everything back together, set the minimum air to 450,and set the TPS to .57vdc. There is still a surge at idle...

Also, I started the car with the MAF disconnected and there is no surge. I plugged it in while it was still running and nothing changed. I shut the car off and restarted it with the MAF hooked up and it started surging again. Does this mean the MAF is good? I think it does.
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Old 08-16-2010, 09:55 PM   #14
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Re: TPI surging when warm

I had a similar problem, when I started my car, it would idle fine, as it warmed up the idle would go up and down, up and down, eventually the idle would peak and valley so severely it would stall the car...

I asked a guy (neat living in Flint, MI) who actually wrote service manuals, and he suggested looking at the ECM temperature sensor located in the front of the Base, under the plenum in the front... Since I had no codes, it was worth a shot... As it turned out the sensor was stuck and it worked great when cold because the sensor was reading a fixed temperature, the further the engine got away from that point the more it was trying to compensate...

Keep in mind that there are more than one temp sensor on the engine. One controls a Fan, one sends a signal to the ECM and a third sends a signal to the gage...

It was cheap like $12.00... back in 2001...

John
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Old 08-16-2010, 10:17 PM   #15
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Re: TPI surging when warm

I replaced that sensor 6 months ago (CTS). I wish it was a $12 or cheaper fix.
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Old 08-18-2010, 08:14 AM   #16
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Re: TPI surging when warm

I ordered a new throttle body and MAF. While I wait for them to get here, i figured I'd do one last thing. I double checked my base timing. I set it at 6 degrees. No change still surging.
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Old 08-19-2010, 04:30 AM   #17
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Re: TPI surging when warm

my 89 tpi just did the same thing. it was the maf, no codes , check light, nothing. just started runnin really bad. spent 2 days going over everything. ive had this car for ten years,never acted like this.. checked injectors hat.. 17-18 ohms theyre stock. changed dist cause i had a spare, 8 new rapid fire #2s, ohmed out all 9 8mm msd wires, checked blaster coil, tps, iac, pulled throttle body and cleaned it, did vacuum leak test, put it all back together and it started right up, ran ok but now i had a check engine light .. looked around and the maf was unplugged... pluged it in and it died.. 170 later from oreileys done. why no code is beyond me. she runs better now, almost 250 k on it. hope this helps. spent hundreds of hours on this rig..
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Old 08-19-2010, 07:46 AM   #18
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Re: TPI surging when warm

That's great. It's nice to see someone fixed their problem. There are so many threads where people haven't fixed their problem. Some have ended in carburetion... Not gonna happen. Carburetion spells DEFEAT.
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Old 08-19-2010, 04:40 PM   #19
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Re: TPI surging when warm

Well, I fixed it. It was the O2 sensor. Runs like a dream now.

Anybody want to buy a MAF and throttle body? LOL
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Old 08-19-2010, 06:00 PM   #20
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Re: TPI surging when warm

i'll give you 5 bucks shipped haha J/K. hmm my car is doin the same thing man as soon itll run rich at ilde to 2000 rpm then i go over that it feels like all 8 cylinders are kickin in an it goes good, i was thinkin maybe my fuel press regulator is shot, which 02 sensor was it?
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Old 08-19-2010, 08:44 PM   #21
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Re: TPI surging when warm

Quote:
Originally Posted by shep236 View Post
i'll give you 5 bucks shipped haha J/K. hmm my car is doin the same thing man as soon itll run rich at ilde to 2000 rpm then i go over that it feels like all 8 cylinders are kickin in an it goes good, i was thinkin maybe my fuel press regulator is shot, which 02 sensor was it?
there is only one. it's on the drivers side exhaust manifold. i thought about it being bad. i even mentioned it in the second post so i bought a new a week ago, but i didn't have the socket to swap it out. i was bored today and decided to tinker with it. instead of spending $10 on the O2 socket, i made one out of an old 7/8 inch deepwell socket.

what sort of troubleshooting have you done?

Last edited by stealth908; 08-19-2010 at 08:47 PM.
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Old 08-19-2010, 08:49 PM   #22
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Re: TPI surging when warm

By the way, thanks to everyone for their help.
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Old 08-28-2010, 12:31 AM   #23
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Re: TPI surging when warm

I'm glad you got it fixed, regular maintenance of parts will keep your car running to it's best potential. There needs to be a sticky thread (if there isn't one) with a list of maintenance schedules
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