99 Rodeo 3.2 hunts, stalls Code P0101-0102

This problem started out intermittent with the first code P0102 Mass or Volume circuit, low input. As the problem became more frequent the code became P0101,
Mass or circuit range performance problem and then it was no longer intermittent but refused to idle without foot on accelerator pedal, would hunt and stall.

I replaced the Mass Airflow Sensor and aircleaner element. Checked the connector and cable to the loom for bad connections, (visual for brecks etc.) could find no obvious problems. Unplugging MAF sensor makes no difference in helping poor performance except one time it starting racing at about 2K rpms after restarting it after unplugging the MAF. It would sometimes do that after it was first started but does not do that anymore.

Did notice something odd when engine is shut down there is a destinctive sound of hissing air heard between the back of the upper engine and the firewall. It does not sound like intake leak as the noise is high on the firewall like its coming from one of the solenoids or vacuum lines on the upper plenum but only after you shut the engine off. Once in awhile it will idle as normal and I listened very carefully for an intake leak sound but could not hear anything . On the rare occasions that it will idle normally, it idles very smooth, not like when the intake was leaking (rough) prior to having it fixed last year.

I do not believe it is intake gaskets (again) as I have had them replaced twice, a year apart, the last time just a year ago. The code for the intake leak was P0300 – P0303 and another that indicated a lean condition on one bank of cylinders.

It does not sound like the MAF signal is getting to the PCM or the ECM because of a leak somewher between the the MAF and the intake manifold. Does the 3.2 V6 Rodeo have a MAF relay?

If any body has any ideas I sure could use some help. My diagnostic equipment consists of digital multimeters and other assorted continuity testers. Nothing exotic like laptop diagnostics. Thanks

Jimsrodeo

This might help you.

http://www.obd-codes.com/p0101

Thanks for the solid info. I'm going to spend some time today troubleshooting all the vacuum lines, the MAP and even the manifold for leaks if I can get to idle.

Jimsrodeo

I checked everything out visually and found nothing but a possible 1/8 in vacuum line that may have fallen off the Induction air control valve or possibly the fuel pressure control valve.
I pulled on this line and it seemed loose but its hidden under a bracket and I could not tell for sure whether it was on or off. I did inspect the line and replaced it. At first it didn't seem to make any difference but after a few minutes it started to idle normally.

I then took a propane torch (unlight) and passed it around the base of the intake manifold ports to check for leaks. Could find no leaks although you can't get to the inside manifold surfaces.

Drove it and seemed fine, shut it down waited a few minutes and restarted. It started racing at just over 2k rpms but after a few minutes settled down and started to idle normally again. I will not know if anything has changed until I start It tomorrow when its cold but it still doesn't seem right.
It has done that before and then gone right back to stalling and spewing lots of black smoke on cold start ups.
The black smoke is also a mystery but it subsides after a few minutes of running. I thought bad injector but it idles too smoothly for a leaking injector. Number six injector was replaced about two years ago along with a fuel pressure regulator as It missed during idle and was hard starting. Any ideas on the black smoke at cold start up now?

Where is the MAP located? I am going to try and check that next.

Thanks,

Jimsrodeo

Checked everything I could except I do not have a scanner that can check realtime engine controls like MAF and MAP. It still is stalling, hunting etc.

The black smoke it spews on cold startup rough idle (like it's trying to clear puddled fuel from a leaking injector) is troubling as it seems to run fine above 2k but does not smell right even when on those rare occasions when it's idling smoothly. Is there a possibility that the idle air control valve could be causing this problem? If it wasn't allowing the proper quantity of air at idle (either too much or too little) would that trick the MAF and give the P0101 code? Could black smoke on start up be enrichment is way off the charts because no idle air is getting in and choking the engine? Too much air would cause it to race at 2k or above (which it has done after it has been run up to temperature and shut down for a half hour or so and restarted).

Please help me out here, I'm running out of Ideas.
Thanks,
Jim

If one of your injectors was leaking, you would have little to no residual fuel pressure after a period of time. Before starting it in the morning or after it's been sitting long enough, check the schrader valve on the fuel rail and see if there is any fuel pressure. You also want to check your fuel pressure regulator. If it's a vacuum type, pull the vacuum hose and see if there is fuel in it. That should be on the opposite end of the fuel rail relative to where the fuel line connects. Something that might help you visually see if you are losing fuel pressure would be to buy a cheap fuel pressure gauge from Harbor Freight and attach it to the fuel rail schrader valve. Run the truck and shut it down and leave it long enough for it to develop the symptoms then check the fuel pressure gauge and see if it's dropping. If the fuel pressure regulator is ok and you're losing fuel pressure, it must be a fuel injector leaking down.

Can anyone direct me to some free, online fuel system, vacuum and wiring diagrams for 99 Rodeo V6 3.2 DOHC engine? Also I am especially interested in some diagrams or drawings that intake runner system that uses two diferent sets of butterflies or runners for low and high RPM operation.

Before I had the intake manifold gaskets replaced last year, under full throttle acceleration, it would spin up to about 3500 RPMs and then it felt like an extra set of pistons would kick in and would actually start to pin you back in your seat. It was amazing the an engine that small in a vehicle as heavy as a Rodeo could pull that strong from 4000 RPMs all the way up to 6500 RPMs.

After these guys worked on it last year it was never the same. It seemed to run OK but it no longer had the increased acceration after 3500-4000R PMs. I took it back but they told there was nothing wrong with it. They screwed something up when they put it back together but I can't seem to find what they did.

I read that the DOHC 3.2 utilized this dual runner or butterfly system to take advantage of both low and high RPM tuning that small displacement, high revving DOHC engine really like. This corresponds with the outstanding performance the 3.2 had (coming on the cams @ 3500 RPMs) before these guys replace the intake gaskets. I have a feeling if I can repair the hunting and stalling, the lazy performance prior to the hunting and stalling ,will also be cured. Anybody have any ideas how these two problems could be tied together?

I will test for a bad injector as soon as it gets little wamer. Friday it supposed to get up into the low forty degree mark unlike today which the hightemp was about 12 degrees.

If it is an injector that would account for a lot of the problems i.e. hunting and stalling. I still dont know why I am getting the MAF code P0101. It doesn't seem like the MAF could be affected. Rich fuel trim maybe or missing cylinder which is what I had the other time an injector wwent south but it did not show a code until it was really bad. This will still idle, on occasion, fairly smooth and run pretty well but it will just start stalling and hunting unexptantly. I really do hope it is an injector.

Jimsrodeo.

Try your local public library website. You might need to get a library card if you don't have one. Our local library has free automotive repair information.

Try your local public library website. You might need to get a library card if you don't have one. Our local library has free automotive repair information.

Got a library card yesterday but have not done a serious search for tech data yet.

I checked the injector pressure 55lbs so I have eliminated a bad injector.

I think I have narrowed it down to the idle air control valve.
Even when it wont idle and hunts, it will run well just off idle If you keep your foot on the throttle only slightly and it runs fairly strong low and midrange.
It acts like a carbureted engine that has a bad choke pull off dashpot. Black smokes when cold as the pulloff wont open the choke butterfly slightly to let just a small amout of air past it during warm up.

I supect the idle air control does the same thing. lets a small amout of air in during cold enrichment when the plenum intake butterfly is closed and establishs the correct enrichment F/A ratio and fast idle parameters.
If it wont open to let the correct amount of air in during warm up, it will surely run rich and stall until the idle air control valve decides to balance the fuel mixture during warmup.

Now that warmer weather has settled in for the last few days (30s and 40s) I am not having the black smoke problems but still the intermittent stalling and no idle. When it does decide to idle it is smooth and steady and if I keep my foot on the throttle only slightly when its having idle problems, I can keep it idling smooth

Is there a way to test this control? They cost about sixty bucks to replace. I dont want just be a parts replacer. I have already replaced the MAF and air cleaner and spent a lot of time testing.

Thanks

Jimsrodeo

Does it have an IAC valve? Most of the "drive-by-wire" cars I've seen have eliminated this since the ECM can simply use the main throttle valve as an idle control. Is the inside of the throttle body clean? There might be just enough crud in there to keep it from idling properly. You should be able to open the throttle valve by hand and wipe it out with a shop rag.

Have you tried pulling off the IACV and cleaning it? All you need is a carb cleaner. It's not a complicated part. I don't know if any way to test the part unless you have Tech 2.

BTW, I believe Gizmo posted a link to the 99 shop manual. Search for his SN and look under his posts.

Does it have an IAC valve? Most of the "drive-by-wire" cars I've seen have eliminated this since the ECM can simply use the main throttle valve as an idle control.

Thanks for your reply.

It is mounted on the top of the throttle body at a right anlge to it. The shop that worked on it a few years ago replaced it (aftermarket unit) when they worked on it.

As it turned out it was a bad injector that time so all they were doing was parts swapping. He called it an idle control motor.

I did remove the inlet duct and checked for crud and it was pretty clean as they replaced the IMG only a year ago.

I found parts of a shop manual that says clean it and then remove the relay/fuse to the PCM or ECU for minute or so, replace and start and let the PCM/ECU reset and adjust the idle. I am going to do that today as it should only take about five minutes.

Once I get that straightened out I am going to find out what they did to it at the last place that replaced the IMG as now those secondary intake runner butterflys are not opening (99 3.2 DOHC) after 3600 RPMs @WOT.

I think they replaced the linkage wrong or the vacuum motor or control may be bad. Its in a real bad place between the Int plenum and firewall. Can only see it with a mirror but I can get my fingers on the linkage parts and they will not move. I am probably going to have to take off the upper plenum cover to get at it. I will need a shop manual first.

I downloaded an Isuzu manual (two Parts at 100 m each) from Rapid Shares but the damn thing is in an "*.RAR " format and it says only the Windows Media player will open it. The media player won't play it until I find the right codex or something and Windows is claiming ignorance about the codex. Everyone else wants lots of $$$ for a good shop manual and this down load was free.

Thanks for your help and I will keep you posted on this.

Jimsrodeo

Have you tried pulling off the IACV and cleaning it? All you need is a carb cleaner. It's not a complicated part. I don't know if any way to test the part unless you have Tech 2.

BTW, I believe Gizmo posted a link to the 99 shop manual. Search for his SN and look under his posts.

Thanks for the info.

I took of the AIC and the pintle as well as opening were covered with carbon, and it looked like it mght be sticking. It looks like a motor with a worm and sector set up that moves the pintle in and out of the idle air orfice. Very precision. It would appear the slightest amount of carbon build up will start to cause problems with correct metering of idle air.

Anyway cleaning it and then pulling the fuse to the ECM for minute, made a tremendous difference in the way it improved idle. That probably was the culprit all along. If the IAC was sticking in the cold start enrichment position after warm up, the MAF may have thought it was an intake leak and woudn't read correctly.

If the IAC would stick completely closed (which it probably does with throttle opening and cruise speeds) upon start it would smoke black from (cold startup) the exhaust until such time at it would start to open and balance the A/F ratio. The thing may have been damaged because when I first started it after cleaning, it idled very slow (200 RPMS) and then picked up to normal rpms for a cold motor and then settled down after a few moments of warm up. I shut it down and started it up this morning cold and it raced at about 2K for about 30 seconds and then went back down to normal. I pulled the ECM fuse again for about a minute and let reset. This I am told will let the ECM recalibrate the idle air corrections. Started back up and viola! normal RPM and the exhaust smelled correct. I will see how it runs for the next few days but I believe that was the problem along with a dirty MAF.

Thanks for your help.

jimsrodeo.

It has one. It really is a idle control motor.
I took of the AIC and the pintle as well as opening were covered with carbon, and it looked like it might be sticking. It looks like a motor with a worm and sector set up that moves a tapered pintle in and out of the idle air orfice. Very precision. It would appear the slightest amount of carbon build up will start to cause problems with correct metering of idle air.

Anyway cleaning it and then pulling the fuse to the ECM for minute, made a tremendous difference in the way it improved idle and ran in general.

That probably was the culprit all along. If the IAC was sticking in the cold start enrichment position after warm up, the MAF may have thought it was an intake leak and woudn't read correctly. If it was stuck completely closed as it would be after reaching operating temperatue and off idle, it would stall and then black smoke upon cold startup enrichment. Also would race after it was warm and you would shut it down and start back up within an hour (IAC stuck open).
Seems like that was it but I am going to drive around a bit before I claim success.

Thanks for your help

jimsrodeo