BOTTLEFED

iTrader: (1)

I have had many problems and I am just now finally getting them worked out, one by one.
I just bought a used reprogrammed ECU that fixed many of my problems but there are just a few nagging things wrong.
I did some searches but nothing fit my description exactly. It did help me narrow it down to my question.
Here's the problem:
My car starts fine and runs OK but the idle is rough and high (1100-1500rpm). However I believe this to be a problem related to my engine being on its last leg; I only have 12-15 in. vac. at idle and less than 95psi compression in both rotors. Now then, I have an air/fuel ratio meter and as the car warms up, the meter reads from lean at first, to off the scale rich within a few minutes. It doesn not matter what the temp is; when the car is started, it reads lean and soon climbs to extremely rich very quickly, especially if I get on it too soon. The car boosts fine and seems a little sluggish (I really have nothing to compare it to since I bought the car dead), but mainly I contribute this to the overload of fuel.
Anyway, after some searches and studying the manual, I narrowed it down to the pressure sensor. So I did the test from the manual and found an odd reading. Warmed up at idle the sensor voltage reads 4.96VDC. With the hose off, it reads 4.96VDC. And any other condition I tried from the manual, I got 4.96VDC.
Thus, my question (finally), is this reading a problem with the ECU sending this voltage to the sensor or is the sensor bad and calling for this voltage constantly? Or is the engine just running so badly that the ECU and press. sensor are doing everything they can to keep the motor running?
Sorry for the long post, but if I can get this fixed my car will be ready for a rebuild. I would like it to be running electronically sound before I start with the mechanicals.

BicuspiD

Sounds like the sensor is bad if it doesnt change vlaues at all, but who reprogrammed the ECU? For what mods?

BOTTLEFED

iTrader: (1)

I'm not sure who reprogrammed it but the fuel map is changed and the ignition retarded for the normal mods (DP,MP,catback,intake,etc). I was told the car would run fine even without those mods. It also came with a Superchip but currently only has the stock chip in now, I have not tried the Superchip in it yet since I only have K&N air filter replacements right now.
Thanx for the reply.

DaleClark

iTrader: (55)

If the idle is rough and high all the time, that's VERY likely a vacuum leak. Common culprits are bad lower intake manifold gaskets and injector grommets.

To find out for sure, get a can of starting fluid. With the car idling, VERY slowly and carefully spray the starting fluid around where the leak might be. If there's a vacuum leak, the engine will suck the starting fluid in and rev up/smooth out. Remember, starting fluid IS quite flammable, but it dries quickly and doesn't leave a residue, which is a Good Thing.

BTW, a vacuum leak is any air leak between the throttle body and the engine. The earlier FD's used paper intake manifold gaskets that warp and fail over time - the new part is metal, and VERY hardy. It's a bitch to change it, though!

Good luck,
Dale

BOTTLEFED

iTrader: (1)

Thanx for the suggestion, I have not considered vac. leaks since I replaced all the vac. hoses with silicone lines. I have done the starting fluid trick before but not on the LIM and my injector seals are new. Are you talking about seals between the rail and the housing?
Also, is there supposed to be a gasket between the TB and the elbow? I have one between the TB and the UIM, but not there.
thanx again