99 ford ranger with a 2.3. Vehicle starts and idles good, it will rev up and hold the rpm, but when you let off the gas it will die out. Compression is between 110 and 130 on all cylinders until it dies, then it drops to 20 psi. Oil pressure is 50 psi at idle and goes up to 65 yo 75 when reved. Timing marks line up and the belt has been replaced. Not sure where else to go with this, it has been at several repair shops to no avail.
You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.
January, 4, 2013 AT 2:23 PM
When it dies it loses most of the compression and free spins. I let it sit for a few minutes and it fires right back up like nothing happened. The iac has been replaced. What do you think about the valves sticking when it gets revved up and it cools down then fires?
January, 4, 2013 AT 2:56 PM
You didn't say that the first time. You are going to have to do some testing during that few minutes to find the problem.
All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.
Every engine requires spark, fuel and compression to run. That's what we have to look for.
These are the basics that need to be tested and will give us the info required to isolate a cause.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
Once you have determined which of these functions has dropped out,
you will know which system is having the problem.
January, 4, 2013 AT 4:29 PM
The injectors pulse and has spark when it dies. I put sea foam in crankcase and put some in the brake booster line while running and it seems to be better. Not sure if that is helping or if it is the engine getting warmer that is changing the performance. When it dies now with the engine at operating temp, it will start up within 30 seconds of dying instead of waiting 3 to 5 minutes.
January, 4, 2013 AT 4:30 PM
The fuel pressure is within spec and it does hold after it dies.
January, 4, 2013 AT 4:31 PM
Sounds like you need to drive around with a fuel pressure gauge attached.
January, 4, 2013 AT 4:47 PM
Something your are telling me can't be true or the engine would be running.
January, 4, 2013 AT 5:57 PM
I tested spark again and that is good, the noid light blinks afterit dies as well. The fuel pressure is between 63 and 65 psi runnning and does not drop off until the motor is dead. When it drops off it goes to 30 to 35 psi. As soon as it dies I crank it over without turning the key off and it instantly jumps to 65 psi again. It dont matter if I cycle the key a few times and crank or just continuosly crank it takes a bit to start. When it does start it from continuos cranking it acts like lack of fuel. It will stumble a bit before it takes off good. The warmer it is the more normal it operates. I changed out the oil pump first because it was at 95 psi and was 30 psi over spec, so I thought the valves were being hung open by the high oil pressure. Now it is at 60 psi at idle cold and drops to 30 psi warm and it starts easier after it dies. The only thing that is odd is the compression drops when it dies and thats why I thought the oil pump having to much pressure was the cause.