98/3.6 Problem Starting Warm. Oil And Idle Bounce While Idle.


New Member
Apr 11, 2017
Howdy! First post here!

I have a problem with my niece's 98 Stang. When it gets warm, sometimes the idle will freak out and act like its going to die. Same time the oil "gauge" freaks out and starts bouncing! That happens at lights or parked. After we start driving it, that goes away tho.

Once parked and return to the car after 10-15 mins or so, it is sometimes hard to start or wont start at all! (it will after cooling off. )

It ONLY happens warm, which is odd to me.

She says it seems to only happen when the gas tank is UNDER half full. I made sure to double check that with her. Another odd thing.

Also says no "Theft light" is blinking at any time.

I told her to check the fuel reset button in the trunk, and she will get back with me on that, but if thats bad, wouldn't it NEVER start at all?

The only code it throws is... crap.. I forget, but its the one saying it has a vacuum leak possibly. We think its the leaky/grimy valve covers that I don't want to mess with tho. And it shouldn't affect the No Start issue,... RIGHT? lol

I've replaced the coils, wires, plugs, AND got a stealership Fuel Pump in it after original died a few years back.

Dad keeps thinking its the pump again, but it didn't display this behavior before, and it seems to me its some kinda electrical fault. Maybe a relay or control module?

I've searched the intertoobs and found nothing exactly like what this is doing, so I turn to the experts here!

I should get the car Fri afternoon to run tests etc, so what should I look for? I do have a code reader that can give some real time info btw, but it only throws the above code, nothing for PCM, ECU, etc..

BTW, I'm an old VW bug guy, that moved into Civics. Rebuilt several engines, and fixed several things on the family fleet of varying heritage, but this has us all stumped!

Thanks all!
  • Sponsors(?)


New Member
Apr 11, 2017
Well, she didn't listen to me, and instead of letting me have it all weekend, she took it to a Stealership, where they charged her $150 and still didn't figure it out.

They did say the O2 sensors were out, and the pump was working perfectly the whole time.

The codes we got (they didn't give her any, or she or dad didn't ask for them) from before this, were:


Now, these relate to the purge valve and the O2s, but if that would cause the hard start problems, you would think the dealer would know that.

He did say that he had this once before, but didn't remember what caused it, or the cure of course..

Thanks, hope someone can help for next time I get the car to look at!
Thread starter Similar threads Forum Replies Date
M Warm start problems... but wierd o.0 Fox 5.0 Mustang Tech 5
S Warm idle/start problems. Fox 5.0 Mustang Tech 5
86T-Top Warm engine start up problems 1994 - 1995 Specific Tech 3
Strype problem still... cranks but no start after warm sometimes? Fox 5.0 Mustang Tech 8
cmb91LX Warm start problem, NOT IAC SN95 4.6L Mustang Tech 4
svasica starting problem when car is warm?! Fox 5.0 Mustang Tech 14
F Won’t start outside of neutral unless given gas Fox 5.0 Mustang Tech 5
1990slow50H Starting issue, electrical problem? Fox 5.0 Mustang Tech 5
K Engine 89 mustang lx 2.3 Starting problems 2.3L (N/A & Turbo) Tech 11
F Electrical New ride - old keyless start problems Fox 5.0 Mustang Tech 4
S 72 electrical problems (click no crank) Classic Mustang Specific Tech 1
O start up problems on my 65 with a 302 1965 - 1973 Classic Mustangs -General/Talk- 6
0 02 mustang starting problems... SN95 4.6L Mustang Tech 1
R Start Problem 1996 - 2004 SN95 Mustang -General/Talk- 4
N Engine 2001 Mustang Bullitt Starting Problem SN95 4.6L Mustang Tech 4
X Electrical problem, Need help! 1965 - 1973 Classic Mustangs -General/Talk- 6
9 Microsquirt with strange cold start problem Digital Self-tuning Forum 5
T (Solved) 97 GT 4.6 Starting problems SN95 4.6L Mustang Tech 13
L Engine Rough Idle at Start, Possible CMCV Vacuum Leak 2015+ Specific Tech 0
M Mustang 2002 Idle/ starting the car when the engine is hot problems. ( help ) 1996 - 2004 SN95 Mustang -General/Talk- 8
P Engine Need help! hot start problem 88 lx Fox 5.0 Mustang Tech 35
K Engine '87 GT cold start problem after working on a/c??? Fox 5.0 Mustang Tech 11
9 Engine 1990 5.0 manual crank/no start Fox 5.0 Mustang Tech 11
I Engine 1991 Please Help -No Start No Click Starter Problems Fox 5.0 Mustang Tech 15
8 87 5.0 GT new owner having starting problem Fox 5.0 Mustang Tech 6
S 87 5.0 GT new owner having starting problem Fox 5.0 Mustang Tech 1
H Engine 2.3l 1988 mustang lx cold start problems and bad idle. 2.3L (N/A & Turbo) Tech 1
M Replaced Heater Core, Now Anti Theft Is On SN95 4.6L Mustang Tech 6
C Starting Problems Fox 5.0 Mustang Tech 5
O Loud Noise When Starting And Pressing On Gas 1996 - 2004 SN95 Mustang -General/Talk- 2
Mooney35 Electrical Problems 2004 Mustang Gt SN95 4.6L Mustang Tech 2
S Starting Problems Fox 5.0 Mustang Tech 13
Mj Garcia Fuel Fuel Pressure Starting Problem !please Help! Fox 5.0 Mustang Tech 4
T Foxbody Won't Start After 15-20 Minutes Of Being Used!! Fox 5.0 Mustang Tech 20
J 14,000 Mile 2006 Gt Hot Start Problems! 2005 - 2009 Specific Tech 4
M 2002 Mustang Won't Start...please Help 1996 - 2004 SN95 Mustang -General/Talk- 1
M 2003 Mustang Gt Starting Problem Cranks No Start First Try SN95 4.6L Mustang Tech 3
jon_95GT SN95 Trouble Starting Out Of No Where 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 10
R Starting Problem 1965 - 1973 Classic Mustangs -General/Talk- 11
T Starting Problem 92 5.0 Fox 5.0 Mustang Tech 2
R Starting Problem 1965 - 1973 Classic Mustangs -General/Talk- 3
S Starting/charging Problems 1994 - 1995 Specific Tech 0
GEAR JAMMER 86 03 Mustang Gt 4.6 Starting Problems 1996 - 2004 SN95 Mustang -General/Talk- 0
Caydink1998 Please Help! Battery Problems..? The Welcome Wagon 3
S Electrical Crank No Start Problem In My '04 SN95 V6 Mustang Tech 1
tca7291 Engine Arrghhh! Cold Start, Surging/stalling Problem Fox 5.0 Mustang Tech 33
J 88 Mustang 306 Mildly Modified "another No Start Fuel Pump Problem" 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 10
J 91 Mustang Starting Problems Fox 5.0 Mustang Tech 1
J Engine 99 V6 Intermittent Starting Problems SN95 V6 Mustang Tech 3
2 Starting Problem. Acts Like Dead Battery But Isn't Fox 5.0 Mustang Tech 2
Similar threads