Changed everything I could, still slow acceleration. Help Nistech or anybody~!

[RatedR]

Just tryin my luck at this section, the KA section seems dead...The car has great pickup when its cold, when it heats up, it makes this crackling/rattling noise coming from the engine (only under load). But when the fan kicks on and everything's all warmed up, it lags like I'm going uphill. Gets to the point that the car cant even beat a bigrig with a trailer.

zerothread?id=119631

Just like the other thread states, I've replaced the fuel filter and fuel pump. Air filter is new, spark plugs are NGK Iridiums, dist cap/rotor and wires are all fine. Set base timing (at idle) to 20 degrees btdc. Just seams like the car wont accelerate as well once its under some heat. Feels like the car is starved for either air or fuel but I've addressed both issues. I hardly think it could be the spark plugs, I dont want to replace a new set just to find out it isnt the problem. Its definitely heat related, I'm hoping it wont continue during winter, but would like to fix it before. The only code the car is throwing is 32 (EGR), which theoretically shouldn't affect acceleration like this.....

NISTECH or any others, would appreciate any advice. Thanks~!

-R

[NISTECH]

Check your O2 and your coolant temp sensor and its connections.

[RatedR]

Hey Scott, thanks for the info. Just wondering though, how would either being defective cause the problem? I understand the o2 sensor (leaning out) but how about the coolant temp. sensor? Also, wouldnt the coolant temp. gauge be affected by the defective coolant temp sensor?

[NISTECH]

The coolant temp could be giving an erronious reading telling it its colder then it is and over richening the engine causing the plug to fuel fowl. No the gauge would not be affected as it uses a different sensor.

[RatedR]

Checked both the coolant temp sensor and the throttle position sensor (just thought I should). No luck, I'm straight lost. Could it be my fuel pressure regulator? How about my plugs? Could they be the wrong kind and have not enough operating temperature rating?

[NISTECH]

hook a volt meter up to your O2 when it happens see if it is going below 0 volts or stuck at a low voltage. Check it while holding the engine at 2000 rpm. May also be an airflow meter problem.

[RatedR]

Thanks for the help in diagnostics Scott~! Here's an update:

Changed a vacuum line that went from the EGR to the BPT. Cleared the 32 code and it never came back(the check engine light).

The car still lags though, I'll do the o2 sensor voltage check. How would I know if its an air flow meter thats messed up by revving at 2000? What am I supposed to check for?

[NISTECH]

Sorry for not being more detailed. The o2 is checked at 2000. I made the assumtion you may have found the MAF checks I have posted in the past. you check its voltages at idle. Should see 3 different voltages from it. 12 volts,1.3 to 1.5 volts and less then .2v. If the thrid one is higher then .2v you gotta splice in a better ground for that wire. The test is done at idle. both sensors are checked while they are plugged in.

[RatedR]

I tried to check the MAF, I wasnt able to get a voltage reading. I did, however, manage to get a resistance reading but only 2. I dont know how to get the third one. I got 1ohm and 6 ohms. So that would make 12v, 2v, how do I get the third voltage? I only see 4 prongs on the MAF, but the 4th one doesnt seem to work. I know the 1st and 2nd are live (positive), the last one is the ground (Thats looking at the maf upside down-attached to the intake pipe and looking over it). I havent checked the o2 sensors.

[NISTECH]

Resistance will tel you nothing. You need to check it while its hooked up and running [under load] You back probe the pins while its plugged in.

[RatedR]

Scott, correct me if I'm wrong, but I figured that running with the o2 sensor disconnected would eliminate it from the list of possible faults IF the problem still comes on??? I tried this, went around with the o2 sensor pulled off and it didnt gain the power back on, it just stayed luggging around. But when I tried the same thing on my 91(my own) 240sx, it didnt affect the performance at all.....does that mean its not the o2?

[NISTECH]

You have ruled out your 02 as being the problem. When you unplug the O2 sensor you are putting it in open loop. Meaning it is reverting to a cold engine state. This still doesnt tell you if the o2 might have a problem but it is not the cause of your problem. You really need to get those voltage readings off the MAF to proceed. OR you could swap parts from your car to this one and use process of elimination. If the MAF doesnt fix it then try the ign coil, If that doesnt fix it try the distributor and so on. That is the alternative to using a voltmeter to test components.

[joelv1]

i am having the same problem, but my ecu set a code 13(engine temperature sensor circut). when it is cold it runs great, after it gets hot it won't pull more than 3500 rpm. i just changed the timing chain, head gasket, a leaking freeze plug, and the cylinder head temperature sensor. i have checked the o2 sensor as described and the MAF was replaced with another out of a running car.

[NISTECH]

Which temp sensor did you change? The 2 wire one is the coolant temp sensor. It is not reading correctly so your car is running extreamly fat when its warmed up. If you did do the 2 wire one then you also need to clean its connector of any corrosion and tighten the female terminals in the connector so they fit better on the sensor pins.

[RatedR]

Been trying a bunch of other experiments, I tried disconnecting a couple of connections. I dont know the first one I disconnected, but it gave me great results without rasing the rpm. Good power throughout the rev to redline. I noticed that the power went away again, but a lot less frequent. Then I tried the TPS, that also gave great power, but the revs would stay around 1700 rpm. What is that one connector for? I've included a pic.

Good catch Scott, the wife's hatch does heat up very quickly. Is that a good indication of the temp sensor being bad?

PS - I did some maintenance work today, I noticed that there's a loud hissing noise coming from the intake mani. After splashing some water around that area, I couldnt see any bubbles....any thing around there that could be causing the noise?

-R

[NISTECH]

My last post was in response to the other poster. The gauge indication on the dash is not the same sensor the ECM uses for engine control. As long as her car isnt over heating you should be ok. In the summer the car will warm up to op temp much quicker then in the winter as its starting temp is already on the warm side.

That connector you disconnected goes to your FICD, AAC and air regulator. Laymens term idle control valves. You completely eliminated all idle control when you unplugged that. The air regulator opened up as a result of a loss of power to the bimetal shutter inside. This would have given you a higher idle. By disconnecting the tps you opened the circuit to the ECM and the system went into base mode. If the idle circuit connector was plugged in and your tps wasent your idle should have dropped to base idle. Which should be around 700rpms, not the 1700 you stated. If that is the case you need to attempt to lower the base idle by rotating the idle screw in till you achive that setting. If you get the screw all the way in and it is still idling high you have a vaccum leak somewhere. Also while the TPS is unplugged you should shoot your timing and see where it is at since you are in the mode to do that. Keep in mind when you unplug stuff like this for testing you are triggering codes in the ECM.

[NISTECH]

hey for the hell of it. Hook up a vaccum gauge, tee it in to a manifold vaccum source, such as your fuel pressure regulator. Make sure you leave the regulator hooked up though. And run enough vaccum line to position the gauge where you can see it while driving. See what you vaccum is doing under the adverse conditions when you experiance them. If you are at wide open throttle trying to accel you gauge should read close to 0 Hg if it has over 15 Hg after a short period of time you might have a restricted exhuast i.e. plugged cat.

[RatedR]

I think there is a vacuum leak. I've got the idle screw adjusted ALL THE WAY DOWN. The lowest idle I can get with everything hooked up is 900. There's also a high squeeling noise coming from the intake mani/fuel injectors. I tried pulling and reseating the injectors/fuel rail but it just moved from the front of the engine towards the 3rd cylinder more.

I'm not sure, but I think I used anaerobic sealer for the intake mani for lack of the gasket. Do you think that sealer isnt good enough for the intake mani and the pressure it's exposed to?

[NISTECH]

I think there is a vacuum leak. I've got the idle screw adjusted ALL THE WAY DOWN. The lowest idle I can get with everything hooked up is 900.

You need to have the TPS disconnected when you do this. Otherwise the ECM will compensate by opening the idle valve.

There's also a high squeeling noise coming from the intake mani/fuel injectors. I tried pulling and reseating the injectors/fuel rail but it just moved from the front of the engine towards the 3rd cylinder more.

I'm not sure, but I think I used anaerobic sealer for the intake mani for lack of the gasket. Do you think that sealer isnt good enough for the intake mani and the pressure it's exposed to?

You need to have a gasket in there otherwise the vaccum will suck in the sealer on decel.

[RatedR]

Okay, did some work on the car yesterday, found out that I did use a paper gasket on the intake mani - that takes it out of the problem string. I did find something else, the o rings (bigger dry ones, not the wet kind) for the fuel injector to seal onto the intake mani was cracked, 2 in fact. So this should be the cause of my intake leak.

After looking at that, I also noticed that the injector on #1 had the plastic tab at the end cracked. I took it out and the whole plastic cap at the spraying end of the injector came off. My question is, how important is that plastic piece? I reinstalled the injector with the o rings, tested to see if it would spray or if it would just dump fuel all over it. It was spraying.

The only thing I'm concerned about is that the o-ring might get sucked in by the engine like Nistech said about the RTV on the mani.

So how about it Scott? Could this be a problem?

[NISTECH]

The cap is there to help "atomize" the fuel. The spray pattern is also effected by this. As far as the oring getting sucked in I honestly dont think it will happen. However I dont see how the orings being cracked would be the cause of power loss on an incline.

[RatedR]

The powerloss isnt on an incline, it just feels like there's no torque. There was a wheezing noise coming from the fuel rail before I pulled them apart. A few of the old mechanics I know at Monument Auto Parts said that it was causing a vacuum leak. Should I still use the injectors I have? Or should I just buy another one?

[NISTECH]

I would replace at least the one thats broke.

[RatedR]

Hey Scott, I took your advice and hooked up a vacuum gauge in the car. The problem went away mysteriously, but every now and then idle gets severely rough. It gets to the point that the whole car feels like its a muscle car..... I get 15Hg of vacuum on idle and close to 0 on WOT. Any suggestions as to what the rough idle could be cause by?

[joelv1]

OK, been busy at work so it took a couple weeks to really work on the car. Here goes: Check all of your vacuum lines. Mine is a '90, when i replaced the head gasket, i crossed 2 lines. On mine there is 1 vacuum control solenoid for the SCV and for some reason there are 2 vacuum control solenoids for the EGR valve, even though three different diagrams say it should only have one.There is a solenoid on the front under the power steering pump and a second one on top next to the SCV solenoid on the back of the head.When the car was cold it ran fine, but when the car reached operating temperature it started idling roughly and had no power over 3000 rpm. Vacuum was being applied to the EGR valve all of the time instead of being reduced as the temperature came up.While hot air was being let into the engine by the EGR valve , the computer set a code 13 for the temperature control circut.I spent 4 hours tracing each individual line and finally discovered the two crossed lines. I switched them back and have been driving the car everyday with no problems for two weeks.