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Classic Car Service
Classic Car Service, Dealership Svc. Mgr.
Category: Car
Satisfied Customers: 4641
Experience:  Over 30 years experience in the automotive field
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2004 Isuzu Rodeo starting issues. Air temperature seems to

Customer Question

2004 Isuzu Rodeo starting issues. Air temperature seems to be a factor it starts every time below 60 degrees, but, it takes about 10 seconds of turning it over to start when air temperature is above 70 degrees. It does not seem to matter if the engine itself is hot or cold. Once running there are no issues.
New Battery, New Catalytic Convertors, New O2 Sensors, New Plugs, New Fuel Filter, New Air Filter, New Ignition Control Module, New Oil/Filter, New Coolant, New Brakes, New Rotors, all in the last 1000 miles (yes I know some of these have no bearing on the problem but I just wanted to list everything that has been done). New Fuel Pump 20,000 ago. Checked all fuses and all were intact. Even swapped relays around. Scanned and no codes in the system. And just based on what I have read on forums I do not smell gas at any point regardless of how hard it is to start.
Is this possibly the Fuel Pressure Regulator or the Oil Pressure Sensor (I've heard this can have an effect)?
Submitted: 11 months ago.
Category: Car
Expert:  Tim Mohr replied 11 months ago.

Hi, my name is ***** ***** is usually caused by a bad coolant temp sensor, or an intake air sensor, have you monitored both of these on a scanner, when its hard starting?

Customer: replied 11 months ago.
Coolant temp sensor was broken at the connector. I went ahead and replaced both and still have the same problem.
Customer: replied 11 months ago.
More importantly, when I turn the key and the starter engages, I can let go of the key, the ignition switch goes from the start position back to the on position as it should, and the starter keeps turning on its own until the truck starts.
Customer: replied 11 months ago.
Since when I turn the key and the starter engages, I can let go of the key, the ignition switch goes from the start position back to the on position as it should, and the starter keeps turning on its own until the truck starts, is it possible that the ignition switch is going bad?
Expert:  Classic Car Service replied 11 months ago.

Hello. Different expert here; please allow me to assist. If the starter is continuing to run with the ignition in the 'ON' position, it is highly likely that you have a faulty ignition switch (the electrical pert, not the key part). I would consider replacement of the ignition electrical switch (that is what the key turns); I do not think you have a key or key cylinder issue; over time, the contacts in the ignition switch can wear out, or lose tension which would allow a cross circuit, and the starter running is a cross circuit when the key is on.

Expert:  Classic Car Service replied 11 months ago.

If you have any questions, please feel free to reply; I will be very glad to help you further.

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Customer: replied 11 months ago.
that would cause the starter to turn over but have a delay in the truck starting, as well as, the stater continuing to turn over when the key goes from the start position to the on position until the truck starts?
Expert:  Classic Car Service replied 11 months ago.

Absolutely. If the computer is not receiving the Key On voltage signal, you may not be powering up the unit properly, or it is not powering up the fuel pump relay. The ignition switch would cause this, yes.

Customer: replied 11 months ago.
Going to get it now, I'll get back to you with the outcome.
Expert:  Classic Car Service replied 11 months ago.

Very good. Thank you.

Customer: replied 11 months ago.
It is still doing the same thing
Expert:  Classic Car Service replied 11 months ago.

That is rather interesting. This is reaching a bit, but, let;s look under the hood for the starter relay. Have someone crank the vehicle, and when the starter comntinues to run, pull the starter relay out of the panel, then quickly refit it. If the starter motor re-engages, you have a bigger problem than just an ignition switch.

Customer: replied 11 months ago.
Pulled relay and starter motor does not re-engage
Expert:  Classic Car Service replied 11 months ago.

Do this: When the starter motor is stuck running, tap the starter relay with a small mallet. Dont whack it, just tap it.

Customer: replied 11 months ago.
I will try that, but, I don't think it is the starter or the solenoid, as in I don't believe the starter is sticking in any way. The starter only continues to turn over until the truck starts then stops/disengages and does not run on after the truck is running. On cool days like today it starts right up as it should. This only seems to happen when the ambient temperature is above 65-70 degrees. Short of the ECU and the harness there really isn't any thing else to replace as the starter is new, except maybe the fuel pressure regulator. I have had checked for vacuum leaks and fuel injector leaks with no results there either. It doesn't throw any codes and nothing unusual shows up on my scanner while starting or while running.
Expert:  Classic Car Service replied 11 months ago.

Can you do an active test on the intake air temperature sensor?

Customer: replied 11 months ago.
Is that necessary? I just replaced it.
Expert:  Classic Car Service replied 11 months ago.

Yes. Defective sensors are always possible. We need to make sure that the values that the IAT sensor is accurate

Customer: replied 11 months ago.
I did a live run on my scanner IAT is at minus 34 degrees. I removed the IAT and jumpered the connector and the temp went to 390 degrees and stayed there even when I jiggled the harness around, so I knew the issue was between the connector and the IAT. I metered the IAT and it was within range. So I took and twisted the pins in the IAT 45 degrees and plugged the IAT back in and it is now at 74 degrees. RPM's dropped from 1050 to 885 at idles and the spark advance went from 19 degrees to 13 degrees. The truck now starts and runs correctly. If the IAT looses connectivity again I am going to replace the harness side connector.
Expert:  Classic Car Service replied 11 months ago.

That is certainly good news! Poor IAT connection....That will certainly do this. Glad you found it. Happy to hear that it is running OK!

Expert:  Classic Car Service replied 11 months ago.

Thanks for choosing Just Answer. It was a pleasure to assist you. I trust my input is satisfactory and meets your expectations. A positive rating for my assistance on your request would be greatly appreciated; thanks again and have a great day