My 4.9 done at the fiero factory is doing this surging type deal. Its an automatic and it runs great, trans functions 100% but after it warms up Ill be driving along and as I come to a stop or slow down the engine doesnt increase in rev but the car feels and sounds like it is surging, almost like the trans is slipping, once the car is stopped it will oscilate like this a couple times the trans feels like it is freewheeling and the tach will oscilate between 1500 rph or so and back to normal idle, then it stops and all is ok. Idles fine, accelerates fine. The hotter the car gets the worse this issue becomes, it was really hot here ther other day and the car just about shut off after going stop light to stop light although it caught itself. I have a friend who says it is most likely an idle control component. Any idea where that would be or if anyone has had the same issue? thanks for the help in advance.

No one has any advice or comment??? wow

Your symptoms sound familiar.

Do you have access to a scan tool?
Mine started having driveability issues when the O2 sensor died. (It also failed the Atlanta e-check, horribly.)

It didn't actually die, it just indicated "full lean", and was causing the PCM to dump in a bunch of fuel.
After it went closed loop (i.e., "warmed up") the BLMs would peg at ~160 on the scan tool.

A quick check would be to unplug the O2 sensor, and see if it still acts up once it's warmed up. (The PCM will substitute default values for the missing O2 sensor reading.)

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Raydar
88 4.9 Formula IMSA Fasback..........................88 3.4 coupe -soon to be something other than red

Read Nealz Nuze! Praise the Lowered!

[This message has been edited by Raydar (edited 06-17-2008).]

O2 (as mentioned)

Idle learn procedure needs done

IAC motor

TCC solenoid (if this tranny has one - it should, but I am not that familar with the 4T60E)

...just guessing based on what you meantioned...

[This message has been edited by Mickey_Moose (edited 06-18-2008).]

ill try that. the exhaust also has a more rich smell to it than what I am used to. Although it doesnt have a cat on it as it has a custom exhaust that ed had installed. The mpg are not so hot either, i dont get on it to bad. but the fuel burn seems to high. Otherwise the car idles and runs very well. I dont have a scan tool but will either invest in one or take it to a shop. will report results thanks for the help!

quote Originally posted by VFR182: ill try that. the exhaust also has a more rich smell to it than what I am used to. Although it doesnt have a cat on it as it has a custom exhaust that ed had installed. The mpg are not so hot either, i dont get on it to bad. but the fuel burn seems to high. Otherwise the car idles and runs very well. I dont have a scan tool but will either invest in one or take it to a shop. will report results thanks for the help!

My exhaust, even with a cat, was bad enough to make my eyes burn.
My fuel mileage was also horrible.

Worth considering, but I'm not sure how it would manifest itself:

If your conversion is running the original GM fuel injectors, there is a very good chance that they are the problem.

I recently sent two sets of Allante injectors to a reputable injector service whom I
have done business with for years. They were to be cleaned, flowed, rebuilt, etc....the normal thing.

I got a call that the injectors were toast. All were either leaking internally, producing way lower than acceptable pressures and patterns, or not working at all.

Seems the GM injectors were made with a type of epoxy that breaks down with today's gasoline components.

Even putting in a new from the box set of GM injectors will only work for a limited time, as the fuel will cause their eventual breakdown.

If you have or obtain a set of Bosch injectors, you will not have the problem.


Didn't mean to throw a 90degree bend into the thread, but it may well be a part of the problem.

David Breeze

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[This message has been edited by opm2000 (edited 06-19-2008).]

Hey David! Whats the cost of the Bosch injectors. For some reason I still think its more of an idle control issue but not sure. I am going to start with 02 and go from there. Can you just swap that out or do you need to reset something in the control module?

Well, yes, the o2 sensor will just swap right out. unplug from harness, unscrew from exhaust manifold, apply fresh antisieze, rethread into manifold, reattach to harness. Undo thebattery while this is going on, and your codes should be reset, I assume.

New Boshinjectors aren't that much, you can shop via google, ebay, rockauto, whatever.

I got a remaned set from my injector service guy for $150.

Isn't shotgun analysis and problem solving fun ?

David Breeze

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