2.4L MFI motor will not idle
02-17-2002, 01:42 AM
#1
Racer
Thread Starter
2.4L MFI motor will not idle
I have a 1973 911T 2.4L MFI. The engine will not idle with out me keeping my foot on the gas pedal. My foot comes off and it dies. Any help?
Thanks,
Scott Harris
1973 911T Targa 2.4L MFI
Thanks,
Scott Harris
1973 911T Targa 2.4L MFI
02-17-2002, 01:54 PM
#2
Addict
Rennlist Member
Rennlist Member
Hello
More details please. ( Sorry offlineworker and don´t have time going trough your profile and old posts )
Cold - warm -hot behaviour ?
have you pulled the hand throttle and on what revlevel is the idle stable ?
Last maintaince and in what condition where the ignition and the MFI ?
Does it smell after fuel or like hot metal ? is your oillevel over max ?
Grüsse
More details please. ( Sorry offlineworker and don´t have time going trough your profile and old posts )
Cold - warm -hot behaviour ?
have you pulled the hand throttle and on what revlevel is the idle stable ?
Last maintaince and in what condition where the ignition and the MFI ?
Does it smell after fuel or like hot metal ? is your oillevel over max ?
Grüsse
02-17-2002, 09:28 PM
#3
Racer
Thread Starter
Roland, It will not idle at all. The only way I can get it to maintain idle is to place a weight on the gas pedal. The gas fumes were so bad that my eyes were burning. The hand throttle does not work at all. The condition does not change even when the engine is at temp. Until I get the RPMs over 1500 the whole car rocks and shakes. Engine rebuilt 550 miles ago, plugs, wires, points, cap, rotor, and coil were replaced. The shop that rebuilt the engine did the best they could with the MFI, but I don't think they had a clue. Also, I noticed that the center injector stack on the right side is making a popping sound. Lastly, the car bolws out smoke at idle and when the gas pedal is depressed. The smoke is a greyish dark color and never stops. I tried adjusting the air mixture screws at the bottom of each injector stack and the popping slowed down but didn't stop. Thats about it. Can you help?
Scott Harris
1973 911T 2.4L MFI
Hello
More details please.
Cold - warm -hot behaviour ?
have you pulled the hand throttle and on what revlevel is the idle stable ?
Last maintaince and in what condition where the ignition and the MFI ?
Does it smell after fuel or like hot metal ? is your oillevel over max ?
Grüsse
Scott Harris
1973 911T 2.4L MFI
Hello
More details please.
Cold - warm -hot behaviour ?
have you pulled the hand throttle and on what revlevel is the idle stable ?
Last maintaince and in what condition where the ignition and the MFI ?
Does it smell after fuel or like hot metal ? is your oillevel over max ?
Grüsse
02-18-2002, 03:37 PM
#4
Advanced
Join Date: Dec 2001
Location: NYC
Posts: 62
Likes: 0
Received 0 Likes
on
0 Posts
Wow, sounds like the shop that did the rebuild got your MFI way out of whack. A good starting point is the MFI technical archive which can be found at <a href="http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm" target="_blank">http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm</a>
If I were in your position, before touching the MFI system, I would first verify that the shop connected everything up properly-- in particular, I would check the transmission grounding strap- if you don't have a good ground to the block, you won't get a good spark in all the cylinders, which will lead to a rough idle and copious amounts of raw fuel being dumped into the exhaust system. Check also the ground strap between your CDI box and the two grounding points on the motor-on the coil bracket and the left chain cover- if it's missing, same problem.
Next step, once you're CERTAIN that it's the MFI system- it sounds like it's running way rich, particularly if there are significant gas fumes. Make sure you have proper ventilation in your work area: rich combustion results in a huge CO content which is highly toxic. Have you pulled the plugs? If you are running super rich, in addition to the gray/black smoke from the exhaust, the plugs will be covered with black soot.
Have you tried disconnecting the cold-start mechanism? I would pull the wire off the solenoid at the top of the fuel filter and tape it up for testing purposes- the cold start solenoid might be dumping raw fuel into the drippers at the bottom of your intake stacks. Unlikely that the cold-start relay could fail in the closed position but you never know.
Another thing to check is the timing of the MFI pump relative to the left hand camshaft- when the two are separated that's a good source of mixture timing issues. Lee Rice's article goes into detail.
When you adjusted the idle intake screws, did you use a synchronizer and get all the stacks drawing the same amount of air? In the absence of another cause of your problem, it sounds like the shop changed the adjustment of your MFI, which means you will have to go back to the beginning and adjust everything according to the "Check Measure Adjust" publication- starting with the throttle plate correlation and working through each step- if you make adjustments to the idle mixture on the pump without having done everything else first there's no guarantee that you will get it running right.
Do you have an exhaust gas tester? I just bought a gunson gastester for tuning the MFI and the folks over on the Pelican Board have a lot of good things to say about them- haven't tried mine yet but am looking forward to it. Pelican also sells a somewhat pricey ($40) set of screwdrivers for tuning the MFI system that could save you the fabrication time.
Good luck, let us know how it turns out.
John
'71 E H-Stock Club Racer
'88 Carrera
If I were in your position, before touching the MFI system, I would first verify that the shop connected everything up properly-- in particular, I would check the transmission grounding strap- if you don't have a good ground to the block, you won't get a good spark in all the cylinders, which will lead to a rough idle and copious amounts of raw fuel being dumped into the exhaust system. Check also the ground strap between your CDI box and the two grounding points on the motor-on the coil bracket and the left chain cover- if it's missing, same problem.
Next step, once you're CERTAIN that it's the MFI system- it sounds like it's running way rich, particularly if there are significant gas fumes. Make sure you have proper ventilation in your work area: rich combustion results in a huge CO content which is highly toxic. Have you pulled the plugs? If you are running super rich, in addition to the gray/black smoke from the exhaust, the plugs will be covered with black soot.
Have you tried disconnecting the cold-start mechanism? I would pull the wire off the solenoid at the top of the fuel filter and tape it up for testing purposes- the cold start solenoid might be dumping raw fuel into the drippers at the bottom of your intake stacks. Unlikely that the cold-start relay could fail in the closed position but you never know.
Another thing to check is the timing of the MFI pump relative to the left hand camshaft- when the two are separated that's a good source of mixture timing issues. Lee Rice's article goes into detail.
When you adjusted the idle intake screws, did you use a synchronizer and get all the stacks drawing the same amount of air? In the absence of another cause of your problem, it sounds like the shop changed the adjustment of your MFI, which means you will have to go back to the beginning and adjust everything according to the "Check Measure Adjust" publication- starting with the throttle plate correlation and working through each step- if you make adjustments to the idle mixture on the pump without having done everything else first there's no guarantee that you will get it running right.
Do you have an exhaust gas tester? I just bought a gunson gastester for tuning the MFI and the folks over on the Pelican Board have a lot of good things to say about them- haven't tried mine yet but am looking forward to it. Pelican also sells a somewhat pricey ($40) set of screwdrivers for tuning the MFI system that could save you the fabrication time.
Good luck, let us know how it turns out.
John
'71 E H-Stock Club Racer
'88 Carrera
02-21-2002, 05:51 PM
#5
Track Day
Join Date: May 2001
Location: Seattle, WA
Posts: 24
Likes: 0
Received 0 Likes
on
0 Posts
I just noticed your post. Are you still having trouble? If soi, when you reply, tell me:
a) was the MFI running reasonably well before the rebuild
b) have you made major adjustments to either the idel adjustment of the part load adjustment on the MFI pump
a) was the MFI running reasonably well before the rebuild
b) have you made major adjustments to either the idel adjustment of the part load adjustment on the MFI pump
02-22-2002, 02:29 PM
#6
Racer
Thread Starter
Bob,
The problems persist. Other than the extreme contamination in the fuel system that prompted the replacement of everything from the tank to the ejectors (except the MFI itself) it ran so-so. The engine did not idle very well until it had gotten up to full operating temp, and even then would not idle above about 600 RPM. But it would idle. When I took the car back from the shop. I would no longer let them touch the car. It would barely idle at all, and would eventually die at a stop light even after being driven over 50 miles. I just replaced the gaskets on my uper and lower valve covers (upgraded to turbo style) and since then it will not idle at all. As soon as my foot is off the gas pedal, it dies. Also, the idle is very rough. Whole car shakes. I do not believe that the part load idle adjustment has been touched, but I could be wrong. The shop apparently had no clue what they were doing.
Can you help?
My home e-mail is snakepittcomics@aol.com, my work number is 270-472-0360 ext.289, home is 731-587-3487. I am about ready to sell the car and start over, mabey throw the money into my 944.
<img src="graemlins/c.gif" border="0" alt="[ouch]" />
I just noticed your post. Are you still having trouble? If soi, when you reply, tell me:
a) was the MFI running reasonably well before the rebuild
b) have you made major adjustments to either the idel adjustment of the part load adjustment on the MFI pump
The problems persist. Other than the extreme contamination in the fuel system that prompted the replacement of everything from the tank to the ejectors (except the MFI itself) it ran so-so. The engine did not idle very well until it had gotten up to full operating temp, and even then would not idle above about 600 RPM. But it would idle. When I took the car back from the shop. I would no longer let them touch the car. It would barely idle at all, and would eventually die at a stop light even after being driven over 50 miles. I just replaced the gaskets on my uper and lower valve covers (upgraded to turbo style) and since then it will not idle at all. As soon as my foot is off the gas pedal, it dies. Also, the idle is very rough. Whole car shakes. I do not believe that the part load idle adjustment has been touched, but I could be wrong. The shop apparently had no clue what they were doing.
Can you help?
My home e-mail is snakepittcomics@aol.com, my work number is 270-472-0360 ext.289, home is 731-587-3487. I am about ready to sell the car and start over, mabey throw the money into my 944.
<img src="graemlins/c.gif" border="0" alt="[ouch]" />
I just noticed your post. Are you still having trouble? If soi, when you reply, tell me:
a) was the MFI running reasonably well before the rebuild
b) have you made major adjustments to either the idel adjustment of the part load adjustment on the MFI pump
02-22-2002, 08:49 PM
#7
plugs foul quickly in a rich running condition like yours. it's impossible to sort out problems with fouled plugs, so they have to be cleaned or replaced as many times as necessary while you sort out the poor running. the oil gets quite contaminated with fuel when it's running rich, so that may need attention too. are the preheat hoses connected from the left heat exchanger to the thermostat? if not, it will run rich for a long time. the main rack seems like it needs to be adjusted a click or three leaner for starters. that's the adjustment under the allen bolt next to the solenoid. hammer out a long skinny screwdriver out of welding rod or a coathanger and engage the screw and feel it click as you turn it clockwise to lean it. (opposite of what you might think). that may even get it idling again.
