Desperate for some help on my Rodeo

[Delano]

Hi All –

2003 Isuzu Rodeo
Manual Transmission
4 Cyl
86K miles

I’ve been having issues for a while now and am just at a loss as where to go from here. For a while I was having issues with fuel delivery and tracked it down to a weak fuel pump and had it swapped out. Another issue at the time is that I would have a hard time starting the car if it was hot outside (weird). I didn’t think these two issues were related but hoped they were.

After fuel pump was replaced it seemed to be running fine but I now wonder if I have the opposite problem.

Current problem:
Car is not running as smooth as it has in the past. No check engine light. Over the last couple of weeks it seems to have gotten worse.

In first gear it will rev high and still feel like it’s dragging as I shift into second. There are instances where I’m driving and take my foot off the accelerator and rpm’s will still surge before coming back down. There has been maybe one or two instances of driving down highway and it hesitated. At this point I’m stressed out driving around town so that may be part of my paranoia but it also feels like a low idle when i come to a stop. It stalled on me only once.

What is really telling in all of this, and why I think I have the opposite problem now (too much fuel), is that the main symptom these days is that I can drive it to work – stay there all day – drive home at the end of the day and if I need to go back out the car will not start. It cranks but will not turn over. Before I had the fuel pump replaced I could start it up with some starter fluid. I tried that the first time this happened thinking maybe it was a bad replacement but it didn’t start the car.

I have:
1.) Cleaned the throttle with cleaner (was a bit gunked up with all the starter fluid i had been using )
2.) Cleaned IAC and verified it is still moving by turning key over when i pulled it from TB
3.) Changed spark plugs (one thing to note is that when I pulled one of the old ones I thought I could smell gas on it. I have since pulled the new ones out but did not see the same with them).
4.) Changed Oil
5.) Changed a couple of the vacuum lines (one from crank case to TB and another from TB to evap something)

I have not done the ‘check for vacuum leaks’ test with some sort of cleaner (can i use TB cleaner to do so?) so I guess that could be a possibility but I’ve changed the ones connecting to TB not sure where else to look.

Could the Throttle Position Sensor be bad if I’m not getting a CEL? Actually, I did get a code for the TPS yesterday but when I turned the car back on after checking code and the CEL was gone. I assumed that maybe I got some dialectic grease on the connector from my gloves since I had put some on the plug boots when cleaning everything off but maybe it’s an intermittent problem?

REALLY sorry for the long post but I really do not know where to go from here or how to start to try and dig into what could be the problem. I am so frustrated at this point. Any help would really be appreciated!

Thanks to anyone who goes the trouble of reading all of this!

Topic

[dan]

hey bud ill see if i can help you here

just because the idle air control moves does not mean its moving properly

does your car have a fuel regulator? sometimes if the fuel regulator goes bad the car can experience a rough idle and cause a rich condition… the way too test this is too plug in a fuel pressure gauge and remove the vacuum line and see if fuel pressure spikes
[video]http://https://www.youtube.com/watch?v=peh7-pFycyc[/video]

you say its a issue during a hotter day could be a intake air temp sensor causing some issues plug your scan tool in and see if its measuring viable intake air temps.

i would see if there are any history codes stored and that could narrow things down

there is also this
http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

and this
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Delano]

thanks so much for the reply! Was out all day with the family yesterday but will try some of the these things today. I’ll start by checking the FPR. I did swap it out about 6 months ago thinking maybe that was the problem originally but who knows.

I did check for vacuum leaks before heading out yesterday and didn’t find anything so I believe that is out as a possibility.

I have a very basic scan tool so not sure about testing air intake. What would I be looking for if it is possible with my scan tool?

There are no codes in history other than the P0122 (TPS) it threw a couple of days ago.

Thanks for the links!
Reading through them I’m wondering if maybe I have a leaking fuel injector since I did see fuel on one of the spark plugs I swapped out before putting the new one in. Could it just be a failing O ring?

Doing the Power Balance Test, can i just pull the boot off the spark plug one at a time? It’s easier for me to access that.

Thanks again so much for the assistance!

[dan]

hey bud

the intake air temperature sensors primary function is too measure the temperature of the air too make very small adjustments in air fuel mixture and ignition timing, a cooler air charge is more dense and requires more fuel too equal out a good air fuel mix, and hotter air is less dense as the air malicules are spread farther apart, in this instance less fuel is required… if your intake temp sensor is telling the engine intake air temp is 30 degrees F and its 80 degrees out its going too run rich.

a way too test this is to have a scan tool that reads live data, if you don’t have a scan tool that reads live data do this.
[video]http://https://www.youtube.com/watch?v=1zdqi8UTZdE[/video]

a leaky fuel injector is know for causing rich conditions but mostly in instances where the vehicle has sat for a very long period of time, the fuel injector is partially stuck open and pressurized fuel inside the fuel rail leaks through the fuel injector into the intake or combustion chamber, a way too test for a leaky fuel injector is this.
[video]http://https://www.youtube.com/watch?v=Gkeng1VGgaw[/video]
notice the fuel pressure gauge during the end of the video, you can do this with a regular fuel pressure tester, when you turn your car onto accessory and allow the fuel pump too prime it should pressurize the fuel too a certian pressure, even after you turn the car off the fuel system should hold a certain pressure for some time, if fuel pressure drops at a noticeable rate like you leave for 2 minutes and fuel pressure drops 20-30PSI you probably have a fuel injector that is leaking.

a fuel injector that is cracked or has leaky o rings will typically leak externally rather than internally.

and you can do power balance tests buy pulling one spark plug wire at a time, but WEAR THICK RUBBER GLOVES OR USE CHICKEN PLIERS! because the automotive ignition system puts out between 40,000 and in extreme cases 60,000 Volts, low amps but extreme volts, it wont kill you but it will hurt, man of experience! but i don’t think it will be necessary to do a power balance test.

[EricTheCarGuy]

Great suggestions above but I don’t think you should ignore the TPS. If the TPS was faulty it can cause a lot of the issues you described. If the computer provides you with a clue like that it’s worth looking into.

You might plug in a scan tool that can read live data and work the throttle while you look at the readings. If they’re off and not smooth, then perhaps you have an issue with the TPS. If that’s the case, I would replace it and recheck for the condition.

Keep us posted on your progress.

[Delano]

So did the fuel pressure test and it turned out the FPR was bad so replaced it. Was running better this past week though still idling what felt to me a little low (600-700 RPM). Thought I was doing good but it has been rainy and overcast all week – until yesterday when it was beautiful and sunny … and a bit hot. Went out to start my car at lunch and same problem as I was originally having: won’t turn over when the ambient temperature is hot. Just very frustrated at this point.

Could a failing TPS cause something like this? Could the Crankshaft Position Sensor?

Thanks so much for all the help provided so far!

[Author]

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