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1990 Nissan Sentra 1.6L 4speed - followup on stumble during acceleration

Had a problem with a stumble on acceleration, especially at WOT-

the car seemed like it was losing power, stumbling, low rpms, the car just seemed like it wasn't getting fuel.

THEN, if you let off and gently accelerate the power is back, everything is fine. This is repeatable ad infinitum and is less apparent (sometimes doesnt happen) when the engine is cold but always present at normal operating temps.

it has good fuel pressure, all 4 injectors work, the fuel pressure regulator works properly, the ECU shows 55 - no faults- same as it always does when i crawl under the dash and check for error codes!

it was recommended to check/replace the engine temp sensor and/or O2 sensor. For whatever reason, I want to blame the TPS so I tested it according to the Haynes manual- I followed the test procedure, and the manual claims it should read .5

-1volt at closed throttle, and 4-5volts at WOT- well according to my meter MY TPS reads the opposite- at the closed throttle it reads 4.3? volts and at WOT it reads 1.1 volts. Have I found the likely culprit? Does the Haynes manual have it wrong?

Thanks to all who take the time to read! robbie

Reply to
robbie
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You are testing at wrong place. You are testing between feed voltage (constant 5V) and output. Test is between output and ground.

Sounds like a fuel starvation problem. Really needs a fuel pressure test under load. T a pressure gauge in after filter, on a long hose. Route the hose under back of bonnet and place pressure gauge so it can be seen from drivers seat.

When I had this problem, I went though the whole fuel system. Everything pointed to a faulty connection but I couldn't find it. Then it packed up completely. Power at relay, no power at pump. Then I found the alarm, dry joint and quite well toasted. Some dork had put a

5A fuel pump circuit though a 2A relay circuit and connectors on the alarm. Soldered alarm and wired up external relay.
Reply to
Peter Hill

robbie wrote in news: snipped-for-privacy@g28g2000yqh.googlegroups.com:

If you haven't checked already, inspect any air hoses leading to the throttle body carefully. If they are cracked and open up when your engine flexes the motor mounts as you accelerate, then it may be screwing up the air mixture.

Reply to
Andrew Chaplin

Andrew Chaplin wrote in news:Xns9D26805F941AAbluegriffin@216.196.109.144:

Heh,they just talked about this on Motorweek yesterday...about the air duct from the MAF to the throttle body cracking and opening under motor torque.

Reply to
Jim Yanik

How about a blocked cat converter? My 87 Pulsar 1.6 had that problem. I'm not sure, but you may have 2 of them (the Pulsar did). One at the exhaust manifold and one in the usual location, below the drivers seat If only one, it's in the usual location

Reply to
willshak
Reply to
Andrew Chaplin

In message , robbie writes

The EGR system helps purge the crankcase of fumes and any pressure build up caused by piston blow-by. Doing away with this could cause crankcase pressure and oil leaks.

Reply to
Clive

No. Your thinking of the PCV valve, The EGR recirculates exhaust into the cylinders to lean out the mixture, warm the incoming air, and cool the burn so as not to burn valves

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Reply to
cselby

Mode III faults that result in non 55 code tend to be gross faults like something unplugged or shorted. When the code isn't 55 the check engine light will be on.

Some Nissan ECU's have a mode V - dynamic test. Doesn't store any fault for mode V faults. The flash pattern indicates which system the fault is in.

Sorry I don't have this data for Sentra 1.6, only UK/Euro '89-94 CA18DET. Sentra may be different. CAS missing pulse - even spaced slow flashes on 1.6sec off 1.6sec. AFM momentary spike in output, 2 flashes then a gap, on 0.6sec, off

0.4 sec, on 0.6sec, off 1.6sec. Ignition - signal from primary coil drops off, 4 rapid on/off 0.2 sec flashes, 1.8sec off. These faults can usually be traced to poor connections, tap tests are suggested to locate.
Reply to
Peter Hill

Yes there are 2 temp sensors. One single wire one for temp gauge and a

2 wire one for the ECU. Both will be on the thermostat housing.
Reply to
Peter Hill

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