Q45 stall on startup - new fuel pump & MAF = no change

[caricbrown]

I have a 1994 Q45 that stalls on start-up. If you give it gas it will remain running at a very low RPM. If you let off the gas it will run with loping idle. Misses on acceleration. Runs smooth at 1500, 2500, 4000 RPM, etc. Still has lots of power, and will stop missing once you get the RPMs up above 2000.

New spark plugs = no change. New Fuel Pump, and MAF = no change. I tried bypassing Fuel Pump Control Unit = no change.

Continuing symptoms: Engine starts then stalls without pressing accelerator. If accelerator is depressed engine will run. After a few seconds you can let off accelerator and engine will stay running <500 rpm.

OBD says no faults.

Any ideas? Thanks.

[maxnix]

Welcome to NICO

Any maintenance history? Checked the CAS? Did it ever run correctly?

[Q45tech]

Dirty throttle body and misset/dirty IAC?

What is ambient and coolant temperature when you try to start? Trying to determine if hot wax warmup system is working..............in cold weather should immediately go to 1500 rpm at idle in park.

[caricbrown]

Yes, it has run great for 6 months. This missing/stalling seemed to come and go for the last week or so. It is doing it all the time now.

Temp is in the 50's to 60's. The engine used to run the idle up to 1100 RPM when first started. Now it just dies immediately.

I will try cleaning the throttle body and IAC.

[elwesso]

how are the injectors? I wonder if its getting flooded possibly due to some bad O rings or something? not common but we've seen it before.

[Haitian_King]

Mine does something similar. It idles really roughly like you can see the car shaking visibly.

Between 40-60 MPH, the car seems to jerk unless I press the gas.

What can I do to fix this?

Oh yeah, Do Q's (1992) just start in second? Because it accelerates like crap until i hit like 25 MPH.

[maxnix]

Oh yeah, Do Q's (1992) just start in second? Because it accelerates like crap until i hit like 25 MPH.

All before 1993. Why 1993 TCU is so popular for early Q45 owners.

[Haitian_King]

So ican just swap out a 93 TCU and put it in my 92 with no hassle?

How difficult is it to do this?

What are the benefits to having this TCU? Other than better initial acceleration.

[DrewQ45]

So ican just swap out a 93 TCU and put it in my 92 with no hassle?

How difficult is it to do this?

What are the benefits to having this TCU? Other than better initial acceleration.

You mean swap out 92 with 93 TCU right? Very easy.... remove foot panel near driver's left foot. 10mm socket and phillips head screwdriver removes the unit.

[Q45tech]

Depending on startup coolant temp the idle should be 1500 rpm and decline from there................1100 rpm should have told you something.........what is IAC cold and warmed up duty cycle 50-30% declining to 10% warmed up.

90% of the time it is dirt [slime from egr/pcv vapor/mixed with air dirt] where it shouldn't be located.

Just like heart attacks people wait for symptoms before a passage clean up.............instead of an annual clean and polish.

[caricbrown]

Okay, cleaning the TB seemed to help the stalling. That or a possible crack int he FICV line.

Thanks for the tip.

I do have the same continuing issue with occasional rough idle, and occasional missing under acceleration. You can drive the car for an hour and never have a problem with missing, or sometime it will miss all day! ANd lately seems to be starving for fuel under hard acceleration (even after new FP,a nd FF) Any ideas here?

Occasionaly we have had fuel smell in the cabin, and what seems to be excess fuel out the exhaust under full throttle. Could this be a FPR or OXS issue? Could this be my engine miss? Thanks again.

[PopPop]

Okay, cleaning the TB seemed to help the stalling. That or a possible crack int he FICV line.

Thanks for the tip.

I do have the same continuing issue with occasional rough idle, and occasional missing under acceleration. You can drive the car for an hour and never have a problem with missing, or sometime it will miss all day! ANd lately seems to be starving for fuel under hard acceleration (even after new FP,a nd FF) Any ideas here?

Occasionaly we have had fuel smell in the cabin, and what seems to be excess fuel out the exhaust under full throttle. Could this be a FPR or OXS issue? Could this be my engine miss? Thanks again.

Sound like U have injector issues and would OHM injectors and try a can of BG44K to see if it helps! If out of OEM specs then hit me up I have used and rebuilt injector units avail!

[DrewQ45]

Okay, cleaning the TB seemed to help the stalling. That or a possible crack int he FICV line.

Thanks for the tip.

I do have the same continuing issue with occasional rough idle, and occasional missing under acceleration. You can drive the car for an hour and never have a problem with missing, or sometime it will miss all day! ANd lately seems to be starving for fuel under hard acceleration (even after new FP,a nd FF) Any ideas here?

Occasionaly we have had fuel smell in the cabin, and what seems to be excess fuel out the exhaust under full throttle. Could this be a FPR or OXS issue? Could this be my engine miss? Thanks again.

When's the last time you changed the fuel filter? Also, you maybe be having an issue with the CAS... (crank angle sensor). The fuel smell could mean that you have a fuel hose leak, usually under the plenum. Does the smell usually occur when it's very cold outside?

[Haitian_King]

i get a fuel smell when it's really cold. Does that mean i have a fuel leak?

[DrewQ45]

i get a fuel smell when it's really cold. Does that mean i have a fuel leak?

Yes. Where you smell gas...there's gas. Usually caused by under-plenum hose leaking. Most hoses under the plenum are hard and cracking by now. My theory is that extreme cold causes the hoses to contract, thereby widening minute cracks/pinholes and allowing fuel to escape to the point where you can smell it. If you notice, as the engine warms, the smell disappears.

My car is also guilty of this and at some point, I'll be replacing my 211K - 17yo hoses.

[96Qowner]

i get a fuel smell when it's really cold. Does that mean i have a fuel leak?

The first hose to start leaking is often a short 3 incher buried under the plenum at the back of the engine. It leads from the fuel regulator to the hard line that feeds the fuel filter, lies sort of vertically at an angle. You can squeeze a ratchet phillips in there and turn the clamp a bit - that'll often fix it until the next winter.

[caricbrown]

When's the last time you changed the fuel filter? Also, you maybe be having an issue with the CAS... (crank angle sensor). The fuel smell could mean that you have a fuel hose leak, usually under the plenum. Does the smell usually occur when it's very cold outside?

FF brand new. I performed a injector ohm test. All 8 were between 21-22 ohms. Checked ECU again, and got a 0304 (CMPS or CAS). Checked the CAS and Pin 2 V = Batt. Pin 3 = 2.36V Pin 4 = .8V Pin 4 seems low, since the book says it supposed to be 1.8V.

I have heard that a leaky injector can cause a 0304, guess I need to pull the injectors???

[Haitian_King]

Aaaaaand you lost me.

[ponzy]

download FSM here:

http://www.phatg20.net/modules...id=62

look for EC - 191 to EC - 207. that i guess will help you out understand the relation of one problem to another and hopefully narrow thoses possibilities that will lead you to the right and proper diagnostic before buying anything...... i would suggest you to buy a laptop-powered consult and a reputable software that will do extra test such as power balance test, mixture-ratio test, etc. right now i do have a problen on my q just after a plenum job 2.5 months ago. i am just busy at work and cant go out and check it. im still awaitng for replies from our knowledgeable moderators and nico supporters as to what is the best software available up-to-date for our car.

good luck............ to us..

[ponzy]

sorry i did'nt read the whole story,, seems you have the FSM already.anyway, good luck......keep us posted....

[caricbrown]

Yeah, I need a consult. The 0304 was from the OBD. Where is the best place to get the USB hookup and S/W?