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engine performance issue

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
1983 - 1992 740
1982 - 1991 760
1986 - 1991 780
1990 - 1998 940
1990 - 1998 960
1997 - 1998 V90/S90

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whathaveidone
Posts: 4
Joined: 30 August 2012
Year and Model: 740 GLE, 1986
Location: British Columbia

engine performance issue

Post by whathaveidone »

hello. i'll keep this short. i have an 86 740 GLE and whats been going on is it will start up no problem, but if you give it gas it dies. it has 175psi in all four, good fuel pressure(tested) good spark(pulled steady 30KV) injector pulse, tune up is in good shape, idles pefectly normal. any ideas? thanks!

precopster
Posts: 7543
Joined: 21 August 2010
Year and Model: Lots
Location: Melbourne Australia
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Post by precopster »

The leads in my 740 were a source of engine breakdown. I tried different brands until I found one that would stay on. Where did you measure the 30KV was it at the leads or at the coil? Is the idle microswitch on the throttle adjusted to close when throttle returns?

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lummert
Posts: 1381
Joined: 29 January 2008
Year and Model: 760 1988
Location: Portland Indiana, USA
Been thanked: 26 times

Post by lummert »

If this is a turbo car check the intercooler piping and hoses for leaks.
1988 Volvo 760 Turbo Wagon

whathaveidone
Posts: 4
Joined: 30 August 2012
Year and Model: 740 GLE, 1986
Location: British Columbia

Post by whathaveidone »

Thanks for your input. i can hear the micro switch click when i move the throttle linkage, and i have ~30KV at all leads. this is a non turbo model and i repaired all vacuum leaks last night when i removed the wiring harness to repair some suspect ground connections, and some deteriorating casings. running rich, replaced ECT today with no improvements.

russellengineering
Posts: 36
Joined: 12 March 2010
Year and Model: 940, 1993
Location: atlanta

Post by russellengineering »

Hi Whathaveidone,

Is the throttle body clean and working correctly along with the throttle position switch? I just figured if it starts and idles fine the TPS or dirty TB could make you stall out.

Good luck,

Dave

whathaveidone
Posts: 4
Joined: 30 August 2012
Year and Model: 740 GLE, 1986
Location: British Columbia

Post by whathaveidone »

I cleaned the TB last night with no improvements, TPS just seems to be a couple of switches, one for idle, one for WOT, and both are functioning. fuel pressure is at 53psi at idle and around 60psi if i pull off the vacuum line. if i pull off the ECT then start the car i can get about 2 strong full throttle revs in before it falls on its face again?

whathaveidone
Posts: 4
Joined: 30 August 2012
Year and Model: 740 GLE, 1986
Location: British Columbia

Post by whathaveidone »

okay, car is fixed! after checking everything i found the MAF was bad. replaced and it fired up SOLVED!!

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