Cole

1986 951 ran well last time I had it out but now has a flat spot/falls on its face.

First gear seems to pull clean through the rpm range.

Second pulls until about 3k and then just sorta goes flat. Boost still shows on the gauge, it just kinda won't go Still kinda pulls through the rpm but almost feels like the wheels or clutch let loose. (Bt they haven't, just the best way I can describe the feeling)

Also idles a bit rough now, kinda bobbles up and down around 5-700rpm, doesn't stall.

I've looked for vacuum leaks. Replaced all the hoses a few years ago with a Lindsay kit.

Exhaust seems solid everywhere. But sometimes you get a gas/exhaust fume type smell in the car.

Thoughts?

951Saga

Have you looked at the spark plugs, injectors serviced, fuel pump and pressure good? Just a start...

Cole

Plugs, injectors, fuel filter all replaced with the vacuum lines just a few years ago. Haven't checked the pump or pressure.

Black51

+1 I MEAN SPARK PLUGS!!!

Sorry

951Saga

Sent used injectors to WitchHunter, came back great. After a DE session, poor idle and exhaust leak, I pulled the crossover pipe/ manifold to reveal possible lean cylinders. Confirmed injectors 2 and 3 were faulty with a flow test. The injectors had been in use for about two years, very few miles though.

Take a peek at the plugs real quick...

V2Rocket

Take a look at the coolant temperature sensor for the DME, and fuel pressure. I have had similar experiences with those things being at fault - so low on gas in the tank that you couldn't go past a third of throttle without the power just cutting off, engine still running but no power coming out of it...same thing happened with the coolant sensor, couldn't do more than very light part throttle. Would still climb in RPM/speed with low throttle but if you opened it up, it would basically shut down.

Jfrahm

It could also be a bad knock sensor.

Ronin-951

Just when was ... 'the last time I had it out'? Bad Gas will definitely do you in, and cause a stumble and low rough idle. Throw in some Seafoam and a bit of Octane Booster and run the Gas out as much possible before a re-fill.

docwyte

Gotta say it cause you're my friend. Time to LSx it!

Jeff N.

Bascially, check everything. Vacuum leaks, sensors, plug wires, coil, injectors, clean your MAF wire [if you have one], fuel pressure...

Start with the simple ones, take it from there.

jimbo1111

Doesn't like a short block from LR cost like $2000?

Cole

Yeah, it does not get driven much. I guess I will start checking those things out.

Don't really need a LSx when I have 3 other big German V8s in the house. One with twin turbos

Rokket

One of the most common problems with the 951's is the dreadful cycling valve. Another relatively unkown problem is the exhaust tubes will crack under the heat shields and acts like an open waste gate.

Have you ran a compression test or fuel pressure test?

Cole

Why would I run a compression test?

Car pulls like a freight train in 1st. It isn't until second gear that it starts to act funny.

Rokket

What about 3rd , 4th, 5th? I fit it sat for a while could have a sticky valve.

A compression test, vacuum gauge, fuel pressure gauge will help you determine whether it is mechanical or engine management issue.

Also, my car blew the wastegate valve out at Sebring...ran great in first gear (back paddocks) as there was virtually no boost required. In any other gear just off idle, the car had a hard time getting out of its own way.