cptmiker

Hello all I am sure this has been discussed more than once but I am unable to find the answers I am looking for. So here goes

Seems to be random missing and or Fuel injectors not Fire'ing. But Constant like a chuge ONLY when Warmed UP
NO ERROR CODES FROM ODB1

What has been done and tested
Full rebuild 30 over
rebuilt head 7120
Compression tested and good
Leak down tested and good
New CPS from Napa
New temp senders both
New Distributor from Napa
New quality cap rotor Plugs and Wires. Copper plugs
New O2 sensor
Cleaned TB- and IAC.
New Echlin Map sensor tested and working correctly.
Tested temp on Cat In 299 out 199 after 20 min run time ( I Know this is not enuff time and temps should be higher (Suspect but was not able to run to hotter temp due to poor performance Missing hick ups and at 2000+rpm and under load only when warmed up
Oil Clean Water Clean No cross contamination.
Fuel pressure holds steady at 31psi at idle as well as higher RPMS runs at 39PSI with Vacuum removed from regulator. Holds PSI at 31 PSI and slightly climbs to 41 when not ruining from 5 Min.
Checked all vacuum lines for leaks as well as Intake and TB for leaks None found. Vacuum is at 18 to 20

What has not been Done
Test IAC
Test TPS

cptmiker

OK I tested the Map sensor and it was bad no voltage change when applying a vacuum to it per the test procedures and had correct voltage without vacuum. So I replace and tested the new Map and it works correctly. I am still having same issue Idles just fine runs fine when cold but when at full operating them it is missing and runs poorly I connected a spark tester from the coil to the cap and notice when it runs really bad it seem that spark is not consistent from the coil to the the cap. I can see visable missing sparks.

tjwalker

Ignition coil itself is suspect. They can be tested for both primary and secondary resistances with a meter and a manual but as you are having a specific condition symptom, testing might not be accurate so I'd replace it. New coils are not expensive and easy to install.

Testing of your throttle position sensor would also not be a waste of your time. Here is some information that I put together a while back on the TPS.
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

cptmiker

Thanks That was my next testing spots as well as the ECU connector.

cptmiker

TPS testing completed
.6v closed
3.6v Wide open
Smoothtransition with no jumping when let off

Coil tested
Primary 1.2 ohms
Secondary 12.12 Both sides
this is a new ACCEL 140021 Ignition Coil

tjwalker

Primary should be 1 ohm or less, not that concerned though about 1.2 ohms. Secondary should be between 6,000 ohms and 30,000 ohms. At 12.12 do you mean 12.12 thousand ohms??

Testing still may not be conclusive here of the coil. If you test a component when it is not symptomatic (and it's difficult to test the coil with engine running when you are seeing symptoms/issues when the engine hot and also being under secondary ignition load), the coil may test within spec but still be faulty.

I'm not saying the coil is the root cause of your issue...but what I am saying is this. To conclusively rule it in or out and this is easy enough to do, I would install a different coil it to see if that changes anything. I will say personally that I have had very poor luck with fail rates of Accel coils and I won't install them or recommend them. Even though they have always worked out of the box for me, my experience is that many (not all to be fair) fail early. An OEM style coil provides all that the stock 4.0 liter engine needs. This is a process of elimination and IMHO, your coil not ruled out just yet.....half an hour and a different coil will tell the story. If different coil has same symptoms, you move on but you have confirmed another piece of hardware as good. Tell me what's good is a big part of figuring out what is bad.

The two sensors that can suffer from thermal (heat related) failure are the crank sensor and the cam sensor, the crank sensor much more suspect to heat failure. I know your crank sensor is new (what brand is it??) and I know you have a new distributor which houses the cam sensor but new hardware fails frequently or is D.O.A, way more than most people would think.

cptmiker

COIL is ACCEL 140021 Ignition Coil

I retested the 12.12 K ohms

Will be swapping out the Coil with the original one that came with the car It was swapped out since this was a new rebuild.. Have new CPS and anuther new NTK TPS coming in the mail. The distributor is a new one from Napa

The CPS was from Napa as well. NTK I believe I have a new NTK on order.

cptmiker

I do not have the original Distributor it was returned as a core charge very proud of the cores 80.00 charge for not returning it.

cptmiker

Replaced Coil with Known good coil and no differance.

cptmiker

Well All said and done here was the fix.
All sensor coil spark plugs cap rotor wires. Injectors cleaned and tested. Compression was 145 in every cyl and leak down was great. The final resolution was a bad computer ECU. I pulled the computer out of my 95 which is compatible and installed it in the 91 and all symptoms went away. put back the original computer and all symptoms came back. So the issue was the computer.