Gauge Problems

[Scream'nCobra]

I posted this a while ago but didnt get much feedback, nor any solutions. So i will try again. My friend and I put in a new cam. And after that, the car runs better than ever, but whenever i go above 3500 RPM's, all the gauges drop. The tach and speedometer both drop to 0, the battery drops to 0, temp stays at 'C' and oil stays normal. The gas gauge goes to 1/2 a tank. Mileage and trip odometer do not move either. Anyone have any idea what could be the problem? I need all the help i can get.

Thanks,
Andrew

 

[Dano]

I'll keep a close eye on this one. My '95 temp gauge gives me fits ... it rises and falls when the lights are turned ON & OFF (oil press. too)!!

There seems to be a common electrical problem here. I've made several posts here and at the SCOA forum, but haven't been able to get a firm diagnosis!

Will be looking for any answers that follow this post. Perhaps the in dash electrical system in the '94 & '95, or just the '95 has a major problem.

Good luck ...

Dan

 

[ohlarikd]

Not that I see any obvious correlation - but exactly at 3500 rpm, the IMRC plates kick in and open up. Maybe there is some sort of wiring problem when the car went back together? Just purely a guess based on coincidence with RPM readings...

Derek
98 Cobra Vert

 

[Scream'nCobra]

It isn't always exactly at 3500 rpm, sometimes it is 3000 or even 4000 rpm. But it is always in the 3500 rpm area. What do the IMRC plates do? This problem is really weird, but i need to get it fixed otherwise i cant go to the track.

Andrew

 

[ohlarikd]

Your car has 32 valves, but only half the intake valves operate under 3500 rpm (estimate, by the way). This is to promote turbulance in the airflow and improve low end power. At higher RPMs, all valves open up. I should say the Intake Manifold Runner Control (IMRC) plates open up and allow air to flow to those extra valves.

There is wiring that goes to a solenoid in the engine bay that opens and closes the valves (I guess they are butterfly valves) in the intake manifold. When you took the engine apart and put it back together again, maybe the wiring got cross connected. shorted, grounded, or something. Its a stretch, but I've heard of stranger electrical problems. Check the wiring.

The plates open at 3500, but the gauges, especially the tach, are notoriously inaccurate, so anywhere between 3000 - 4000 rpm is probable....


Derek

 

[Scream'nCobra]

Is this the same in the 5.0's? I notice that you have a 32 valve 4.6, but i have a 5.0 and im not sure if they work the same in this area. Thanks for the quick run down on the IMRC plates tho! Do you think you could direct me to a specific plug or wire than i could mess around with?

Andrew

 

[ohlarikd]

ahhhhhh crap. I didn't notice that you had a 95 5.0L. There are no IMRC plates on that engine - only the 32 valve engines... Sorry for sending you down that path!

Derek

 

[Scream'nCobra]

Any electricians out there? I really do not want to take this to a mechanic. Any input is needed.

Andrew

 

[fiveoh]

Scream'n Cobra do u have the stock computer on there? I have heard of guys having problems similar to this after doing such mods as cam, heads and intakes. This is just a guess but it could be your problem.

 

[Scream'nCobra]

Yes the stock computer is in there. Check my other thread (94/95 5.0 guys) Could that ground wire have anything to do with it? Maybe i ought to buy a PIH anyway....

 

[Scream'nCobra]

Well yesterday i drove the car and decided to push it hard for my cousin and it didnt blow the fuse. Drove it again today and it seems to have fixed itself. I can finally go all the way to 6000 rpm's! Well, im very happy that it fixed itself, but it still blows my mind. Thought i would let everyone know...

Andrew