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1999 Spyder GS 4g64 problem

Dmczeke

Probationary Member
4
0
Jun 17, 2016
Woodland, California
Hey guys. Just bought a 99 Spyder GS 5speed 4G64 for a father and son project. No mods yet other than drilled/slotted rotors and a couple inch drop. Fixed a bunch of random stuff so far, but we are stumped on an engine issue. The car starts and runs great when cold, but after it's nice and warmed up (about 3 minutes), the rpms drop way down, the car stutters, almost dies. If I leave it running, it sort of clears up after a few minutes, rpms raise to about 1k, and I am able to rev up the motor with just a small bog/hesitation, but then it might drop way down to 300 rpm again. There is no CEL on. It will run great with the MAF disconnected. I've been scouring the local (Norcal/Sacramento) Pick n Pulls and got some random parts. I tried another GS Spyder ECM with no change. Tried two other MAF sensors, no change. Tried another coolant temp sensor with no change. I grabbed a TPS and cam sensor, but did not try those yet. From my web searching, I've read that maybe the IAC is bad. I couldn't find my version in the junk yards and that part is around $250-$350 at the parts houses. Is there another model car or truck that I can get that blasted IAC off of from the junkyard? Am I going in the wrong direction? Seen some other posts about this problem, but no one has ever given a solution.

Thanks for any info or help that you guys can give.:sneaky::banghead::aha:
 

infam0usdeed

Proven Member
61
5
Nov 20, 2012
North Las Vegas, Nevada
For the IAC, your kinda stuck. I have a Spyder GS too. Your best bet, if you suspect the IAC, test and it make sure it is bad, then see if Miller Import Parts can get you one. I think I got the whole throttle body from them for $55. Tps and Iac included. Need a good cleaning though.

The only issue I've had close to yours was the honey comb on the maf was all messed up. Replaced it with one that had nice honey combs in it. Ran fine after that.
 

spyderdrifter

Supporting Member
5,135
634
Jul 11, 2009
Some where, Colorado
Try looking for a '94-'98 (7th gen) Galant, or a '98-'04 Galant (8th gen). Both of these generations were available with a 4g64 engine, and is probably one of your best chances to find the correct IAC.
 

Christopher Chlebek

Probationary Member
10
1
Jun 19, 2017
Chicago, Illinois
I haven't yet. I replaced the maf, IAC, TPS and map still same thing. On my OBD2 scanner I would get randomly the car goin into open loop even with the temp at 200 degrees. I'm starting to assume if it's the ECU. Only code I have is the p0403. can that effect it in anyway to run like that.
 

spyderdrifter

Supporting Member
5,135
634
Jul 11, 2009
Some where, Colorado
The egr system, which that code reders to, could most definitely give you a vacuum leak and cause idle problems. I would check that out before changing the cam sensor and see if there's any change. It could be a bad egr gasket, dry rotted vacuum line going to it, ect... while checking that system, it wouldn't hurt to inspect the other vac lines for wear.
 

Christopher Chlebek

Probationary Member
10
1
Jun 19, 2017
Chicago, Illinois
So I was trying work on this today and it didn't want to stay running it would just die after 5 seconds. So I decided to take apart the ecu and this is wat I found
 

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Christopher Chlebek

Probationary Member
10
1
Jun 19, 2017
Chicago, Illinois
So I'm back to square one. Put the new ECU and after 5 mins of running, it started acting up again. I'm running out of ideas here. Can anyone help
 

DogWhistle

Supporting VIP
696
268
Sep 13, 2012
St. Paul, Minnesota
It's probably the fuel pump control relay. Classic symptoms. It's not a matter of "if" they fail, it's "when".

We had the same problem on our (father son project) Spyder.

Below is the link to our write up on how to bypass this secondary relay.

http://www.dsmtuners.com/threads/4g64-spyder-gs-fuel-pump-relay-module-bypass.497574/

You'll learn a lot together working on DSMs together. The 4G64 is a great platform to learn on.
 

Christopher Chlebek

Probationary Member
10
1
Jun 19, 2017
Chicago, Illinois
ill try it tomorrow. i really hope this is the solution bc its driving me crazy. well not really driving since it runs really bad and cant take it on the streets
 

pauleyman

DSM Wiseman
6,559
1,733
Nov 19, 2011
oklahoma city, Oklahoma
Hey guys. Just bought a 99 Spyder GS 5speed 4G64 for a father and son project. No mods yet other than drilled/slotted rotors and a couple inch drop. Fixed a bunch of random stuff so far, but we are stumped on an engine issue. The car starts and runs great when cold, but after it's nice and warmed up (about 3 minutes), the rpms drop way down, the car stutters, almost dies. If I leave it running, it sort of clears up after a few minutes, rpms raise to about 1k, and I am able to rev up the motor with just a small bog/hesitation, but then it might drop way down to 300 rpm again. There is no CEL on. It will run great with the MAF disconnected. I've been scouring the local (Norcal/Sacramento) Pick n Pulls and got some random parts. I tried another GS Spyder ECM with no change. Tried two other MAF sensors, no change. Tried another coolant temp sensor with no change. I grabbed a TPS and cam sensor, but did not try those yet. From my web searching, I've read that maybe the IAC is bad. I couldn't find my version in the junk yards and that part is around $250-$350 at the parts houses. Is there another model car or truck that I can get that blasted IAC off of from the junkyard? Am I going in the wrong direction? Seen some other posts about this problem, but no one has ever given a solution.

Thanks for any info or help that you guys can give.:sneaky::banghead::aha:
There is more than one temp sensor. You sure you changed the sensor the ecu reads?
 

Christopher Chlebek

Probationary Member
10
1
Jun 19, 2017
Chicago, Illinois
It's probably the fuel pump control relay. Classic symptoms. It's not a matter of "if" they fail, it's "when".

We had the same problem on our (father son project) Spyder.

Below is the link to our write up on how to bypass this secondary relay.

http://www.dsmtuners.com/threads/4g64-spyder-gs-fuel-pump-relay-module-bypass.497574/

You'll learn a lot together working on DSMs together. The 4G64 is a great platform to learn on.
Hey Thanks man. I haven't messed with it for awhile been busy. But I read that link and I noticed that fuel pump driver module was f... hot. burned my hand a little.
 
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