O.K., here's the deal. I've got a '90 LX 5.0, 5 speed. About a month ago it started idling rough, like the whole car would shake when sitting still. Sometimes when I drive at highway speed, 55-70, and slow to a stop, it will die. I've started noticing the smell of gas now, and can even see it in the exhaust when I drive. My mileage went from 20 down to 9 on my last 2 tanks!! I changed my plugs, and the old one's had gas on the tips. The new plugs did help with the rough idle, but not completely. I was told to check the fuel pressure regulator by pulling the vaccuum line off the top and seeing if there was gas inside, which should tell me it is bad. Tried that last night, and it looks fairly new, and there was no gas inside. I was told to check the fuel pressure by attaching a gauge to the fuel rail, but I don't have one to check it with. Anybody have any advice on what else I could check? I was just told to check the voltage on the iac valve, but is there something else while doing that?
Rough Idle/Running VERY Rich...HELP!!
- Thread starter Glaxtx
- Start date
DTT92LX
New Member
I just had similar symptoms and it was a vacuum leak. My hose from charcoal canister to upper intake split. New hose, all better.
Remove the vacuum line from the fuel pressure regulator and the manifold. Once you have both ends disconnected, blow through it. If the line spits out gasoline, the fuel pressure regulator diaphram is shot and it is time for a fuel pressure regulator.
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html
IF your car is an 88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 88's except possibly the Cali Mass Air cars.
Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at Walmart.
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html
IF your car is an 88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 88's except possibly the Cali Mass Air cars.
Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at Walmart.
oz
Founding Member
How many miles on the car? I wouldn't be surprised if the oxygen sensors need to be replaced. Pretty much any car over 10 years or 75k could stand to get new sensors... although, they usually go bad over time, not all at once.
Another thing to consider is that when one cylinder goes lean, that causes the O2's to read that bank as being lean... the computer sends more fuel to all the injectors until there is balance.... then all cylinders except one are running rich.
If you dropped a cylinder for instance, that would make the o2 read rich (from the unburned fuel) and the car would run lean (as the computer compensates).... so I don't think it's an ignition problem.
It could be from a bad or plugged injector, messed up MAF (reading more air that is actually going in the motor), faulty water temp sensor, faulty intake air temp sensor, vacuum leak.
Since it happened all of a sudden, I tend to believe that the computer is compensating for a lean condition that came on all of a sudden - like the suggestions above. I would actually be surprised if it was your fuel regulator.
Reading the codes should give you an idea of what's going on. If you can't read them, many privately owned repair shops will read the codes for minimal costs (I paid them 1/2 hour labor to read mine before I bought my car).
Another thing to consider is that when one cylinder goes lean, that causes the O2's to read that bank as being lean... the computer sends more fuel to all the injectors until there is balance.... then all cylinders except one are running rich.
If you dropped a cylinder for instance, that would make the o2 read rich (from the unburned fuel) and the car would run lean (as the computer compensates).... so I don't think it's an ignition problem.
It could be from a bad or plugged injector, messed up MAF (reading more air that is actually going in the motor), faulty water temp sensor, faulty intake air temp sensor, vacuum leak.
Since it happened all of a sudden, I tend to believe that the computer is compensating for a lean condition that came on all of a sudden - like the suggestions above. I would actually be surprised if it was your fuel regulator.
Reading the codes should give you an idea of what's going on. If you can't read them, many privately owned repair shops will read the codes for minimal costs (I paid them 1/2 hour labor to read mine before I bought my car).
icarus
Founding Member
my guess would be a vaccum leak or bad egr. Bad egr will cause rough idle, stalling and poor gas mileage. Just something else for you to check.
oz
Founding Member
EGR - that's a possiblilty, although if the EGR is malfunctioning a dummy light on the dash will light up.... When I bought my GT the seller said 'the engine light blinks on sometime, the mechanic said it was a bad EGR'... sure enough - replaced the EGR and reset the computer and the light never came back.
I did have the codes read too and that confirmed the EGR problem (not sure if it was the sensor or the EGR so I replaced both).
I did have the codes read too and that confirmed the EGR problem (not sure if it was the sensor or the EGR so I replaced both).
Check the 10 pin connectors, and the wiring behind and around the back of the intaker. I had this very same exact problem and it turned out to be a short in the wiring. read this thread:
http://forums.stangnet.com/showthread.php?t=486124
http://forums.stangnet.com/showthread.php?t=486124
Thanks for all the advice so far! I just got home and checked the codes. The first time I hooked it up I got a 12 and 13, which would be the ISC (TPS?), and got a code 14. I tested it again and got 11, which is system O.K., and 14. I looked up the 14 and it shows "Ignition pickup (PIP) was erratic - Ignition Systems". What does that mean?
Code 14 - Ignition pickup (PIP) was erratic – the hall effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. You have to press the distributor gear off the shaft to replace the sensor. The pip signal is used for ignition timing and fuel injector timing.
Well, here's the update. I replaced the hall effect sensor, and cleaned the contacts on the salt & pepper shakers. My only problem is I don't think we got the distributor lined up just perfect yet. I drove it and it idles perfectly smooth, but seems like there's no power below 3,000 rpms. Without a timing light, I don't know what it's set at, but maybe someone has an idea on how I should adjust it now. Thanks again!
72bronko said:
Easy things first... Do a cylinder balance test to find a bad injector:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 for everything OK, or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html
For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at Walmart.
trbkrb
Founding Member
I just replaced my distributor also yesterday! I noticed that there is a notch on the stock distributor that is roughly about at the 10 deg stock setting for the timing. I used my light and the notch is just barely to the left of the left side of the distributor hold down. Mine is running fine when stopped now, but it is struggling to run and the exhaust pulses are really hard out the pipes, so I think my cats must be clogged or something due to all the unburned fuel or something. The plan is to change the H pipe tonight.
On a side note, what part of Houston are you in? Have you been to www.westsidemustangs.com ? We are a local group of guys & gals that are a great source of help. We have several Ford technicians and other very knowledgable people on the board. Check it out. Good luck on yours!
On a side note, what part of Houston are you in? Have you been to www.westsidemustangs.com ? We are a local group of guys & gals that are a great source of help. We have several Ford technicians and other very knowledgable people on the board. Check it out. Good luck on yours!
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