4runner running strange/Where to start?

68ChargerJMP

68ChargerJMP

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I have a 97 4Runner 3.4/auto. Over all it runs good but over the last few months, something is not right. It started feeling a little sluggish lately, even though I run a rear mount turbo. It has a slightly unsteady idle, hesitates and stumbles just a little going up a grade. I had a friend hook it up to a good scan tool and the numbers were fluctuating all across the board. CPS, TPS, IAT, RPM, Coolant temp, etc.. were all over the place. They would level out and the next minute, all over the place again. I have been having a 0171 code for a long time and cannot find it. I have cleaned and replaced MAF sensor more than once. Cleaned TB, IAC. Nada, still there. Coolant level is constant and it doesn't smoke, so I don't think its a HG issue. Just recently, it threw a 0120 (TPS) code. I'm gonna start by replacing the TPS and go from there. Any advice? Thanks.
 
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Do the tps but numbers all over the place on a scan could be ecu connections or an ecu itself. Luck. :cowboy:
 
I have thought of the ecu as well. Someone mentioned the alternator diodes could be bad and causing the issues. I have a spare ecu but it's from a 99. Will the 99 ecu work in a 97?
 
No the 99 ecu will not work in a 97. I would check with another scan tool, some of them can be weird or slow to display live sensor data from the ecu. PO171 is a Bank 1 lean code, code be from running lean under boost are you running stock injectors, how much boost, increased fuel presssure and any tuning done? Check for any leaks around the intake mainfold, vacuum lines, intake tube after the MAF sensor. Si ce you can a scan and can read live data from the ecu watch the fuel trims on bank 1 any higher than around 8-10 for a long time confirms a lean condition on that bank. Test the TP sensor and replace it if its bad and calibrating any be needed with replacement. Check the spark plugs for wear and replace if needed. Mine had a slight stumble/sputter on up high acceleration but ran fi e otherwise, worn out spark plugs was the issue.
 
AZ4Running said:
No the 99 ecu will not work in a 97. I would check with another scan tool, some of them can be weird or slow to display live sensor data from the ecu. PO171 is a Bank 1 lean code, code be from running lean under boost are you running stock injectors, how much boost, increased fuel presssure and any tuning done? Check for any leaks around the intake mainfold, vacuum lines, intake tube after the MAF sensor. Si ce you can a scan and can read live data from the ecu watch the fuel trims on bank 1 any higher than around 8-10 for a long time confirms a lean condition on that bank. Test the TP sensor and replace it if its bad and calibrating any be needed with replacement. Check the spark plugs for wear and replace if needed. Mine had a slight stumble/sputter on up high acceleration but ran fi e otherwise, worn out spark plugs was the issue.
Click to expand...

Here's the thing....I only run 5-6 lbs. boost at most and it ran great for over a year. I never had any issues. I never dogged on it at all. I don't think its boost related. What would cause it to possibly show lean on bank 1 at idle with boost out of the equation? Plugs are fairly new, though I probably will swap them out. I just did a boost leak test yesterday and it was fine. No leaks anywhere that I can find.
And to the post above...I changed fuel filters when it first started this and it didn't help at all. The filter I took off was fairly new and was clean as could be. Thanks.
 
68ChargerJMP said:
I have a 97 4Runner 3.4/auto. Over all it runs good but over the last few months, something is not right. It started feeling a little sluggish lately, even though I run a rear mount turbo. It has a slightly unsteady idle, hesitates and stumbles just a little going up a grade. I had a friend hook it up to a good scan tool and the numbers were fluctuating all across the board. CPS, TPS, IAT, RPM, Coolant temp, etc.. were all over the place. They would level out and the next minute, all over the place again. I have been having a 0171 code for a long time and cannot find it. I have cleaned and replaced MAF sensor more than once. Cleaned TB, IAC. Nada, still there. Coolant level is constant and it doesn't smoke, so I don't think its a HG issue. Just recently, it threw a 0120 (TPS) code. I'm gonna start by replacing the TPS and go from there. Any advice? Thanks.
Click to expand...

I've been chasing p0171 Lean code for the past month with the same symptoms-although no turbo. Long term fuel trim would spike to 39%+. I've changed out the IAC, MAF, fuel pump/filter, injectors, regulator, all vacuum lines, plenum gaskets and the A/F sensor and rear O2 sensor (Calif emissions), plugs/coils, still had the code-all denso/OEM and cleaned TB twice. I just replace the A/F sensor (front O2) sensor for the 2nd time and now it seems to have corrected the problem. (I hope-no code showing and no more stumbling).

The front AF sensor/O2 sensor was the only thing that I couldn't say was 100% new as I bought it on ebay (as new) but it didn't come in a Denso box or include gasket so I went to Advance Auto and put the cash for another new, sealed in box one. I assume you have fed. emissions vehicle so it will have two O2 sensors on the exhaust.
270k miles

Hope this helps.

J
 
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Since more than just the TPS was all over the place, I would look for other things first. Wiring? Grounds? Maybe pull the ECU and check for leaking capacitors?

-Charlie

PS. I have a '97 3.4/auto/4x4 ECU just taking up space in the garage if that turns out to be the issue...
 
Ok. So, I replaced the tps and upstream sensor with a known good one from my other 97. Still idles like crap. Any ideas to for the next step other than ecu? Thanks.
 
How's the battery voltage reading (either by the ECU via OBD II or multimeter)? Re-check the ground on the intake manifold by the diagnostic connector.

-Charlie
 
firemanj92 said:
I've been chasing p0171 Lean code for the past month with the same symptoms-although no turbo. Long term fuel trim would spike to 39%+. I've changed out the IAC, MAF, fuel pump/filter, injectors, regulator, all vacuum lines, plenum gaskets and the A/F sensor and rear O2 sensor (Calif emissions), plugs/coils, still had the code-all denso/OEM and cleaned TB twice. I just replace the A/F sensor (front O2) sensor for the 2nd time and now it seems to have corrected the problem. (I hope-no code showing and no more stumbling).

The front AF sensor/O2 sensor was the only thing that I couldn't say was 100% new as I bought it on ebay (as new) but it didn't come in a Denso box or include gasket so I went to Advance Auto and put the cash for another new, sealed in box one. I assume you have fed. emissions vehicle so it will have two O2 sensors on the exhaust.
270k miles

Hope this helps.

J
Click to expand...

Thanks for the reply.....I changed the o2.....no change.
 
68ChargerJMP said:
Thanks for the reply.....I changed the o2.....no change.
Click to expand...

Bummer, fuel pressure regulator? Also, did you just change 1 O2 sensor? There is a belief that both should be changed at the same time along with a battery disconnect/reset.
How about bad/stale gas, I know it's rare today. Our t4r has been code free now for 40+ miles. I don't know if it was the bad forward A/F (O2) sensor that I had to replace twice or the an enzyme gas additive I added due to ethanol & moisture. (I'm not sure if E85 was accidentally put in tank which I doubt but it would definitely cause a lean code in the T4Rs - I didn't fill it up last).
 
Ok...question about short term fuel trims. At idle, mine are around +19.5, at 2500 rpm, it's at 0 to -3.
It has a noticeable hiccup/dead spot at idle that you can see on the scan tool. My other 97's STFT sits at -6 to -9 or so st idle. Could this be fuel pump, injector, or fpr related symptoms? Thanks.
 
Sounds like a vacuum leak somewhere if the STFT is that high at idle. I would inspect in that area next. Vacuum leaks will be most noticeable at idle which explains why you have the erratic idle.
 
Last night STFT were dead steady at 19.5 ....this morning, they were fluctuating from 3 on up and steadily increasing. Never went to 19.5 but it was still not all the way warm.
 
Tonight, I let it warm up good and the STFT went to 19.5 again. So, is 19.5 normal for idle or are we pretty sure that is jacked up? Thanks.
 
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