Engine bogs at ~2500 RPM. PLEASE HELP!
 

Hey, all!

Well, this is a new one for me. :017: Last night as I was driving home, the engine started bogging out when I hit about 2500 RPM. I drove almost the whole way home at 2250 RPM and 50 MPH.

This morning, I started the car and headed for work. The engine revved up fine. There were no issues - UNTIL the car reached operating temperature. After reaching temp., the car bogged out at ~2500 RPM all the way to work. As I came home, same thing. The car runs fine until it reaches operating temperature.

Here's what I've checked. Please let me know if I'm missing something!

Fuel pressure: Normal. I upgraded the FPR in February of this year. Gauge reads fine...

Fuel delivery: Good. I replaced the fuel pump and filters in February, too.

Fuel injection: Good. All injectors are less than a year old.

Intake: Optimal with a clean K&N filter element.

Spark Plugs: Only about 10,000 miles on them. I cleaned and re-gapped them a few months ago. It is the last time I ever buy SplitFires, though. NGK for life!

Ignition Coil: Replaced at same time as the plugs with new, 7mm silicone wires.

Catalytic Converter: Replaced with Hi-Flo (well, hollow :unibrow:) unit a couple of years ago. I really doubt it's clogged. Everything sounds great behind the car (nice clean, exhaust).

Temperature Sensor: Fairly new. Replaced a few years ago. This car is driven often, but not many miles.

O2 Sensor: Could this be a culprit?

AFM: I cleaned this not too long ago when I installed a new throttle body.

I just dropped a bunch of coin on a new transmission for my daily driver (Jeep). I still have another week (at least) before I finish it, so I really need my Z because it's the only running car I have right now. Because of my transmission woes with the other vehicle, I also don't have a lot of money to throw parts at the Z. Just to clarify, this is a normally aspirated engine. Any suggestions? PLEASE HELP! :087:

Thanks in advance for your replies!

James
1980 280ZX

It's either a fuel or spark / timing problem...

I suggest starting with a check of all sensors & connections. Make sure the TPS, AFM, and CHTS connections are snug and free of any grease / corrosion. Also pull the spark plugs & read the tips. Then check the timing. Also, check the coil & ignitor and connections. A common sign that the ignitor is failing is hard warm starts, or sudden power drops while driving.

EDIT... and what do mean by "cleaned the AFM" ? Did you pop the black cover and check the carbon track & circuit board?

Did water get into your engine bay (did you clean it out with a hose)?

Could be that you got the TPS wet and are creating tricking the CPU into thinking the throttle is not where it really is (happened to be when I cleaned my engine bay). If it's wet, just use a hair dryer or heat gun to dry (be careful!). Or, if you can remove it, put in in a bowl of dry rice overnight - that will suck out the moisture.

GL!

NismoPick,

Yup - checked ALL connections and vacuum lines. And yes, I pulled the cover apart on the AFM and cleaned it when I replaced throttle bodies... :017:

Philbert,

Good call! We've been having unusually wet weather lately and I did drive through some water... I didn't think for a second that it would reach that high - but it's a definite possibility. A TPS sending incorrect info to the computer would explain the symptoms... I think I'll try the rice trick! I'll let you know what happens...

Cool - hope that's it!

I remember when it happened to me I was so puzzled, and then someone asked me on my "HELP!" thread if I'd had water on anything. I used hairdryer but since have learned that rice is GREAT for grabbing moisture (saved my alarm keyfob recently after getting wet).

Philbert,

I hear ya'! Rice has been saving phones and all sorts of other small electronics in our household. Funny how I never think about putting car parts in there, too... TPS is in the bowl right now. Hoping to put it all back together tonight...

Did this resolve it?

Yes, it did! Took her for her first drive this morning since reinstalling the TPS. Still rainy as all get-out... Hopefully, I keep the unit dry this time...

That's great to hear! maybe get some electrical tape around the connections to protect it in the future from rain?

Electrical tape isn't going to do much. I don't normally recomend it but in this case dielectric grease would help. People don't seem to realize that grease is not conductive (unless you use conductive grease then you get a short circuit and resistance) and makes a poor contact. It keeps water out and prevents corrosion but it also makes a barrier between metal contacts. So when you use dielectric grease KEEP IT OFF THE METAL CONTACTS. Same as when you use it on the boots of your spark plug wires - on the boot but not the contacts.

If you want to keep water out use heat shrink with a meltable inner jacket.

Just an FYI... some newer Nissan TPS plugs (like from a later KA24DE or SR20DE) will have the rubber "rectangular" o-ring at the inside base to seal out moisture. Just cut it from a junk yard car, and solder it into your TPS harness w/ heat shrink. Or just grab the o-ring if your connector is still in good shape.

just some info incase someone has a similar problem but it isn't the TPS. the Air Flow Meter can cause the same problems. with my 280zx the spring on the AFM wasn't tight enough and it caused it to run so rich that it would not pass 2500+ rpms. the tighter I got the spring the better it ran. BUT, keep in mind that moisture can destroy the internals of the AFM and to clean it out use compressed air and then use silicone to seal the black cover back when you're satisfied with the way it runs and you're ready to put it all back together

great info
 

I power washed my engine bay last night, had to limp it home, was seriously funny, car isn't licensed, I was sure I was gonna see blue lights, dried out the Distributor, but didn't do anything to the TPS yet, I will dry it out tomorrow, and try and find a way to seal it. It would accelerate to about 2500 rpm and then just slam to 500 or so, if you mash the pedal it would just die.

TPS wet
 

My TPS connector was full of water, I dried it out, and cleaned it up, my connector looked like the statue of liberty, all blue with copper oxide. Its a wonder even dry that it was making good contact. After cleaning the car freely accelerates, no bogging or hesitation. Fricfracs kit is perfect for fixing this issue, and many others.