guages to diagnose issues.

[Skeith]

My engine (3.1L MPFI) still hasnt been running great, for the first couple min cold start first time of the day the engine idles rough and stumbles and stalls when i give it gas, after a couple min it seems to run fine.

The idle used to lope but i replaced the O2 sensor last week and now it doesnt lope but seems to miss here and there.

I installed a vac guage and tach to the dash so I can watch the engines RPM and manifold vac when im driving it to find the problem. every time it started acting up I'd pull over hook up a vac tester and start it but it would run fine then. So i figure a permanent guage would be best.

My 2 questions are first, where can I splice in the tach, in my haynes manual on the coil packs there are 5 wires, purple/white, white, tan/blk, black/red and white. Problem is both white wires are right beside each other on the connector, the order as is on the connector is tan, white, white, a space, purple, black. does anyone know which one of the white wires is the tach or the easiest way to find out?

second, the vac guage, it says to drill a hole in the intake manifold to get a ported vac feed for the guage, but i dont feel like drilling, right now its tee'd off the MAP sensor line, I could also T off the vac line that runs to the transaxle and it is ported directly into the manifold, would that give me a better reading?

once these are hooked up then its time to start diagnosing problems.

[bszopi]

The tach white wire is the "C" terminal, or the one next to the open space.

As far as the vacuum line goes, anywhere should be fine, and I doubt there is any place that is better than another.

[Superdave]

Those gauges aren't going to help much, what will help is hooking a laptop up to the car and actually logging the output from all the sensors. You can figure issues like this out really quick.

How handy are you with electronics?

[Skeith]

im quite decent with electronics.

I cant get the tach to work anyway. Hooked it up and I get nothing, the needle kinda quivers when i start it but thats it.

[Skeith]

Got a different tach hooked it up and this one works.

heres what I got.

Vacuum.

car starts and idles showing around 13 inhg, however using my vac tester under the hood it shows 15 inHg at idle. Seems low on both, however it doesnt surprise me that the dash guage reads low since its fed with like 9 feet of 1/4 ID tubing. So it seems to be reading 2 inHg under. when I crank the tester shows the engine pulling about 4 inHg which is in range for starting. This does not register in the dash.

these are all from the dash so the tester would read 2 inHg higher
When i open the trottle in gear the guage dips down to about 5 in Hg then quickly stabilizes at 10 inHg durring acceleration. once I reach a cruizing speed of 60km/hr it reads 15 inHg over run at 60km is about 20 inHg. On the highway accel up to 80km/hr is 10 inHg and over run about 25 inHg.

so the manifold vacuum in general seems to be functioning properly just a bit low. When it idles it holds at about 14 and drops to 13 for a split second when i feel the engine miss. It doesnt always miss, sometimes it idles fine.

The tach readings are pretty good. start up engine is at 1.1k rpm and drops to idle of 800rpm. durring acceleration it shifts at about 2k rpm into second and doesnt go much over 2k under normal accel.

vacuum has got me stumped.
All lines have been replace except the PCV valve line because that involves taking off the intake manifold as its port is right under the intake. Also the Hvac lines IN the passenger compartment have not been replaced, the have been replaced up to the compartment. Also removing a line from the hvac to cause a leak has no impact on idle at all. I was certain that the idle would go up if a leak was suddenly created, which leads me to believe there is a leak somewhere either in the PCV or the Hvac in the cab.

I also noted that when i switch the heat/ac/fan on or off the vac drops about 1 inHg for a split second. but that is hard to distinguish from the engine missing.

Those were with the engine running decently without hesitating, stumbling or stalling. Tomorrow morn on a cold start I will take not of the readings and post back.

But in the mean time does anyone have any suggestion where to start?

I cant even see the Hvac line in the cab after it enters the firewall, it gets lost in the abbyss but somehow has to make it over to the passenger side where the hvac controls are.

[Azrael]

Could be that the EGR is stuck slightly open? The engine usually sounds and idles like it's aggressively cammed when it is and idle vacuum shows a little low. A drop in vacuum is normal when engaging the A/C as the PCM will command higher idle speed with the the idle control valve.

[3400-95-Modified]

Could be that the EGR is stuck slightly open? The engine usually sounds and idles like it's aggressively cammed when it is and idle vacuum shows a little low. A drop in vacuum is normal when engaging the A/C as the PCM will command higher idle speed with the the idle control valve.

Also dependent on the car the VAC sometimes controls the HVAC controls, so that will explain a dip when you turn that on. I know it does on my Beretta.

[Skeith]

I dont know, I know I had an EGR error in the comp before, but I took the EGR apart cleaned the valves and solenoids and tested them, put it back in and didnt see the error since.

Car ran great this mornin. stumbled once when I first gave it throttle and then ran fine all the way to work. stopped for coffee and even after it sat it started and ran again. Though the first start was a hard one. Im kinda wondering if its my fuel pump.
I have a fuel filter I want to change but I cant get the old one off, the threads are seized. Whats a fuel pump supposed to sound like running? mine kinda sounds like one of those toy motors when its supplied with lower than rated voltage.

On the way home though, the car ran like crap. Started fine, but the idle quickly dropped to about 450 rpm and the needle would swind between about 450 - 550 when idle. Idle is the same regardless of whether its in neutral or in gear.
Gave it gas and it imediately stalled. started fine and stumbled a bit out of the parking lot but once I got onto the road it seemed to run alright, though idling low at red lights etc.

I also noticed when making a slow turn i have her a bit of gas to get it coasting very small amount (tight corner) and the vacuum showed the over run at 22, then it droped to 14, swung back up to 22 back down to 14 and then stabilized at about 16 untill it began idling again in which the vac droped to 14. It didnt do that at all yesterday.

also when i pulled into the driveway I reved it up to about 2500 to listen to it and it was shaking more than usual so im quite certain it was misfireing.

Letting her cool right now, gonna pull a spark plug and take a peek in a bit. I thought I may have heard it backfire but it could have been something else i couldnt tell if it came from me or not, no change in vacuum or RPM when i heard the sound though.

[Azrael]

Backfires are generally fueling problems, or at least that's true with carbs. Might be time to borrow a fuel pressure gauge or a scanner to check O2 readings.

[Skeith]

I have a vacuum tester with a fuel pressure guage on it but it only goes up to 15 pounds, so i doubt that will work. i was under the impression FI engines use much higher pressure.

For the hell of it i did use a rag and press the schreider valve on the fuel rail to check for residual pressure and got not even a dribble, so It could be a leaky injector or a bad check valve, though i dont smell any gas under or around the intake I was told leaky injectors usualy result in a smell in the engine compartment.

When I pulled the plugs out from the front bank, i didnt see anything unordinary on the front bank, points are clean no sign or lean or rich running.

[Skeith]

So, I changed the injector O rings, plenium gaskets, TB gasket, PCV valve and the fuel filter.
It seems to run better, has more power and doesnt hesitate as much, still a tad bit in the morning on the first run but nothing like it used to.

Next is to replace the EGR gasket and EGR mounting plate gasket (not sure exactly what its called, the little plate with the stove pipe attached to it.)
i thought the EGR gaskets came in the plenium kit i bought but apparently not.

Also have to change the water pump, a weird sound sort of like deiseling is coming from it so Im sure its on its way out. Also since that will be in progress with the coolant level down, the temp sending unit is probably due for
replacement, and also the TB, I have the TB from the old engine, cleaned 'er up real good.

I noticed the other day the TB, if I pull on the trottle cable and release it completely (with the engine not running) it kinda makes a kerthump noise, where as the TB I pulled from the old engine just snaps shut. Sounds like something is sticking or something, or closing late. Not sure though. planning to get this all done next week. After this, Im not sure what else I can replace on the damn thing.

[Azrael]

If the old EGR gaskets didn't tear you might be able to get away with reusing them. I've done this a few times without any leaks. As for the TB, check that the plate isn't loose and make sure the linkage is stopping on the set screw and not from the plate touching the walls of the TB.